2011 Update Presentation 9_3_10

Smog Check
2011 Update
Goals of this Class
Inspection Procedures
Aftermarket Parts
OBD II Practical Processes
Catalytic Converter Testing
Final Examination
Smog Check
Pre-Test Check List
• Ensure all test equipment is up-to-date and
• Check for vehicle test restrictions and inform
consumer if any apply
• Ensure consumer is provided a proper
• Ensure vehicle is safe
Page 1
Vehicle Identification
• Technician Access
• Vehicle Identification Information
– Using the bar code scanner
– Using vehicle registration documents
– VID communication failures
• Each tech is responsible the accuracy of the
Page 2 & 3
Emissions Tests
• Before Test Conditions
– No safety hazards
– Vehicle is at operating temperature
– All vehicle accessories are off
– Verify proper test (TSI or ASM)
– Verify tires are dry
– Verify vehicle fits on dyno
– Verify vehicle is restrained properly
Page 5
Emissions Tests
• Before Test Conditions (cont.)
– Verify cooling fan is positioned correctly (72°)
– Connect RPM pick-up
– Insert tailpipe probe
– Lower Hood (ASM)
Page 5
Emissions Tests
• Acceleration Simulation Mode (ASM)
– 50/15 & 25/25
– Incompatible vehicle designs
Page 6
“Non-disengagable” traction control
Full time all wheel drive
Too large to fit dyno
Hybrid vehicles
Heavy Duty Vehicles with a drive axle weight that
exceeds 5,000 pounds when vehicle is unloaded
Emissions Tests - Preconditioning
• Vehicle shall be warmed to operating
temperature, and idle for at least 3 minutes
immediately before starting the emissions
• Technicians shall not attempt to superheat the
• Refer to the Smog Check Inspection
Procedures Manual, Page 5
Emissions Tests
• ASM Gear Selection
– Automatic (Drive)
– Manual (Second gear)
– 2500 RPM for 30 seconds
– Idle mode
• Refer to the Smog Check Inspection
Procedures Manual, Page 7
Page 7
BAR Technician Performance
Bureau of Automotive Repair
Inspection Quality
BAR’s strategy to clean the air relies on
technicians properly failing those vehicles that
should fail.
Roadside testing and the Sierra Report both
demonstrate that many vehicles that should
fail the Smog Check inspection are not being
failed appropriately.
Inspection Quality
What are the most common ways to get a failing
vehicle to improperly pass an inspection?
– Not perform required elements of inspection (e.g., timing,
fuel cap, LPFET, OBDII)
– Reset OBDII systems prior to test to clear DTC’s
– Over-condition ASM test vehicles (restart, abort tests)
– Drive an ASM inspection in the incorrect gear
– Direct cheating (clean piping, clean plugging, etc).
Inspection Quality
• Test deviations measure departures from required
inspection procedures as appropriate to the vehicle
Failing to inspect ignition timing
Failing to inspect the fuel cap
Failing to perform the LPFET test
Failing to perform the OBDII test
Resetting OBDII systems without making repairs to get
vehicle to “slip” through
– Restarting or Aborting tests to provide second chance
– Using the wrong transmission gear for the ASM test
Inspection Quality
• Test Deviations – Ignition Timing
– Measures the rate at which each
station fails to perform a timing
inspection when most technicians
indicate that the timing is
– Deviation flag set when a station’s
rate is above average for similar
Inspection Quality
• Test Deviations – Fuel Cap
– Measures the rate at which
each station fails to perform a
fuel cap pressure test when
most technicians indicate that
the fuel cap is testable
– Deviation flag set when a
station’s rate is above average
for similar vehicles
Inspection Quality
• Test Deviations – LPFET
– Measures the rate at which each
station fails to perform the LPFET
when most technicians indicate
that the vehicle’s evaporative
system is testable
– Deviation flag set when a station’s
rate is above average for similar
Inspection Quality
• Test Deviations – OBDII Test
– Measures the rate at which
each station fails to perform a
OBDII test when most
technicians indicate that the
vehicle’s OBDII system is
– Deviation flag set when a
station’s rate is greater than
average for similar vehicles
Inspection Quality
• Test Deviations – OBDII Reset
– Measures the rate at which each
station passes vehicles with the
exact number of necessary
OBDII readiness monitors set in
order to pass
– Deviation flag set when a
station’s rate is greater than
125% of average for similar
Inspection Quality
• Test Deviations – ASM Restart
– Measures the rate at which each
station restarts ASM inspections
– Deviation flag set when a
station’s rate is greater than
125% of average for similar
Inspection Quality
• Test Deviations –
Inspection Abort
– Measures the rate at which
each station aborts
– Abort flag set when a
station’s rate is greater than
5% of total inspection starts
Inspection Quality
• Improper Gear Selection – ASM test
– Manual Trans – test in 2nd gear (Page 7, Smog Check
– Auto Trans – test in drive (Page 7, Smog Check Manual)
– Engine RPM during tests indicates when vehicle in
incorrect gear
– RPM limits assigned by specific vehicle configuration
• Example: 1989 Toyota Camry, 2.5l auto trans
• Limit = 90 percentile + 300 rpm
– Stations disqualified if more than 2% of vehicles were
certified with RPM beyond limits in either ASM test mode
Inspection Quality
• Improper gear selection – example of limit
Engine RPM, ASM 5015
VLT Row 40711
1989 Toyota Camry, 2.5l Automatic
Limit = 90th
Percentile +
300 rpm
Engine RPM
Inspection Count
Inspection Quality
• Improper gear selection example:
– 1989 Toyota Camry, 2.5l automatic
Inspection Quality
• Improper gear selection example:
– 1989 Toyota Camry, 2.5l automatic
Inspection Quality
• Comparative Failure Rate (CFR)– serves as a
basic litmus test for whether a technician is
failing vehicles that should fail.
– Compares the technician’s failure rate to the
industry failure rate for the same type of vehicle.
Inspection Quality
• Comparative Failure Rate
The technician’s failure
rate must be greater than
or equal to 75% of the
statewide failure rate for
similar vehicles.
Inspection Quality
• While the performance metrics discussed thus
far will push performance higher, they can be
– Examples – RPM simulators, entering vehicles as
testable for certain program elements (e.g., LPFET)
and then faking the test results, etc.
• Solution: Introduce a robust long-term metric
to ensure quality over the long haul
Inspection Quality - FPR
• “Follow-up Pass Rate” (FPR) correlates current
cycle pass rates to quality of inspection in the
previous cycle
– Comparison made across similar vehicles (Model year,
make, model, engine size, transmission type, body
shape, time since last inspection, previous inspection
result, vehicle odometer)
Inspection Quality - FPR
• Conceptual example: two hundred 1995 5.0L Ford
Mustangs were high-emitting vehicles in the last
inspection cycle.
– Half were clean-piped, shifted into the wrong gear, or
over-conditioned in order to pass their last inspection.
– The other half were properly inspected, failed, and
then repaired to legitimately pass their last
• Vehicles from which group are more likely to pass
in the current cycle?
Inspection Quality - FPR
• FPR scores reflect probability that a
technician’s vehicles pass at a higher rate than
average in the next inspection cycle
– Scores Range from 0 to 1
– 0 score means we are 100% confident that
performance is below average
– 1 score means we are 100% confident above
– 0.5 means we don’t know conclusively due to
insufficient test history
– New or low-volume technicians assigned 0.5 score
Technician Feedback
• BAR will set up a secure Web page to view
• Will provide technicians feedback on their
• Password protected so technician may view only their
own data
Covered Topics
• How to recognize aftermarket parts during a
visual inspection
• Parts labels, Executive Orders (EO) and links to
verify parts
• Pre 1/1/2009 catalytic converter labeling
• Post 1/1/2009 catalytic converter labeling
• Other approved aftermarket parts examples
• Modified aftermarket parts examples
Visual Inspection
• Vehicle Emission Control Requirements: Technicians must
use all available information necessary to determine the
vehicle’s emission control requirements, including but not
limited to:
• The under-hood emission control label (see section 1.3.2)
• The current emission control application guide
• The emission control repair manuals
• The emission component location guides
• The manufacturer emission control recalls and TSB’s
(Technical Service Bulletins)
• The vacuum hose routing diagrams
• The California Air Resources Board (CARB) aftermarket
parts listings, the aftermarket part label (see section 1.3.2),
and any reliable vehicle manufacturer sources.
Visual Inspection
• If a vehicle is equipped with parts that modify the
original emission control configuration, technicians
must verify whether those parts are CARB approved
or exempted. If the installed parts are not CARB
approved or exempted, and the original emissions
control configuration has been modified, the
corresponding emission controls are considered
“Modified” and the vehicle shall fail the inspection
Smog Check Reference Guide
• Aftermarket Parts Verification Guidelines
Gasoline and Diesel – Appendix G
– Aftermarket Parts Definitions
– Category I lists parts that do not require EO
– Category II lists parts that require EO verification
– Diesel Quick Reference
Visual Inspection(cont.)
• To verify CARB approval or exemption, technicians
must check the Aftermarket Parts Label affixed either
directly to the part or near the part. This label contains
a CARB Executive Order (EO) number that can be used
to verify approval or exemption. With the EO number,
reference the CARB EO parts listings and/or part
manufacturer catalog
• The CARB EO part listings and information about
catalytic converters can be found on the CARB website
www.arb.ca.gov. Technicians may also contact ARB at
(800) 242-4450 if they need additional information
Aftermarket Parts Label
• Note: A missing or illegible APL does not
constitute an inspection failure. In cases
where the label is missing or illegible, the
technician may proceed with the inspection,
provided the parts can be confirmed as CARB
approved or exempted by comparing the part
number marked on the part with the CARB EO
parts listings or the parts manufacturer
Web Links
•All Non-original catalytic converters must be CARB
approved/exempt and are labeled with information
necessary to ensure that installations comply with
California law.
Catalytic Converter Labeling
• Catalytic converters installed before January 1,
New aftermarket catalytic converters and certified used
catalytic converters can be identified by a permanent stamp
or label on the shell of the converter. The label/stamp
should be in the following U.S. E.P.A. format: T/CA/MC
XXXX YYYY. The labels do not include the EO number
• T: Either “N” (for new aftermarket converters), or “U”
(for certified used converters). ARB staff has found that
this character is sometimes omitted on new
aftermarket converters
• CA: Indicates that the converter has been ARB
• MC: A two character code for the converter
• XXXX: The converter’s part or series number. The
number may be longer than 4 digits
• YYYY: The date of manufacture. The first two digits
indicate the month, and the last two the year
Pre- 1/1/09 Labeling Example
Approved in
N = New
TA = Manufacturer
See Website Database
The Converter Part/Serial Number
09 05
This Table Lists Valid Manufacturer
Codes For California
Advanced Car Specialties (RiteCat).
ESW America, Inc.
The Automotive Edge (Hermoff)
Emico Technologies, Inc.
AirTek, Inc. (Catco)
LaPointe Exhaust System
Brown Recycling & Manufacturing, Inc. MC
Miller Catalyzer Corp
Bosal Mexico SA DECV
Car Sound Exhaust System, Inc.
Perfection Auto Prod. Corp
Valina, Inc. (CarTex).
Products For Power
Cateran Pty Ltd.
Walker Manufacturing
Eastern Manufacturing Inc.
TRI-D Industries Inc.
Equipo Industrial Automotriz S.A. de
Tested Products (DEC)
Catalytic Converter Labeling
• Catalytic converters installed on or after January 1,
 Meet more stringent requirements
 Labels include the EO number in large font, presented in
the following format:
Decoding Catalyst Labels
 D-XXX-XX =
This is the ARB approval number for the converter (known as the “EO
number”). Every EO number will begin with “D”. The first three X’s will
be a 3 digit number corresponding to the manufacturer. The last two
digits will be the specific approval number for the manufacturer. The
EO number can be used to obtain information about the approval
status of the converter on ARB’s website in the same manner that
other aftermarket add-on and performance parts can be looked up.
The website address is:
The part number for the converter (assigned by the manufacturer)
 ZZZZ =
The date of manufacture. The first two digits indicate the month, and the last
two the year.
Legal Converters With Laser
Printing And Plate ID
D 280-73
D 280-77
Labeling Example
ARB EO# D-193-86
Manufacturer Assigned part
# 36104
March 2009
Resource Examples
This screenshot shows where to enter the
replacement part EO number into the ARB search
Enter the EO#
here: D-193-86
Left Click Here
EO # D-193-86 Entered Into
ARB Search Engine
Fuel Injection Conversion Kit
With EO - 1979 Jeep Cherokee
CARB EO# D452-2
1979 Jeep Carburetor is
replaced with a TBI unit
Aftermarket Air Intake with EO 2003 Mitsubishi Eclipse
2003 Eclipse EO Sticker
Attached Underhood To
Vehicle Body
This is just one example of many CARB
approved aftermarket parts.
Then Scrolling Down On The EO Page We Find
That The Vehicle And Engine Are LISTED.
Adjustable Cam Gears
Aftermarket Headers With No EO
1995 Saturn Sl 1.9L
Aftermarket Air Intake With No EO
2003 Toyota Celica
Aftermarket Air Intake With No EO
99 Honda Civic
Aftermarket air
intake systemno EO
What to enter into the EIS?
The Other Emissions Related Components category
encompasses emission control systems that are not otherwise
addressed in the visual inspection menu. Other Emission
Related Components include, but are not limited to:
– Add-On Aftermarket Parts
– Cylinder Heads
– Exhaust Manifolds
– Intake Manifolds
– Superchargers
– Thermal Reactors
– Timing Gears and Pulleys
– Turbochargers
Other Emissions Related
• If a vehicle fails the Other Emissions Related
Components category of the visual inspection,
technicians must document, on the VIR, what
emissions system failed.
• Note: The Other Emissions Related Components
field is also used to capture failed test results for the
Visible Smoke Test. For more information, see Smog
Check Inspection Manual section 1.3.4.
Notations on the repair order
• It is necessary to make notations on the repair
order of any aftermarket devices that are
entered into the EIS “other” category.
• If there is no Executive Order (EO), enter as
California Code of Regulations
(a) Test Report Requirements
(b) EIS Access & Tampering
(c) Entering Information into the EIS
(d) Repair Procedures
(e) Testing Directed Vehicles
OBD II Practical Processes
OBD II Procedures
Circuit Testing
Understanding Sensors
Understanding Outputs and Actuators
General Diagnostics Strategies
Readiness Monitors
Mode $06
Circuit Testing
Understanding Sensors
• The Powertrain Control Module (PCM)
performs two distinctive functions
– Performs Voltage Drop Tests
– Performs Logical Decisions based on the voltage
drop test results.
• There are three categories of sensors;
– Variable Resistance
• Has an internal resistor, the resistance value changes
with Temperature, Pressure, Air Flow or Position
– Voltage Producing
• Produce voltage based on engine detonation/pinging,
oxygen content of the exhaust, rotation of the
Crankshaft, Camshaft, Wheels or Vehicle Speed
– Switching Type
• A switch type sensor input is a clear high or low signal,
depending on whether the switch is open or closed
Types of Sensor Signals
Analog Signals
• A variable signal that is
proportional to a measured
• Analog signals are produced by
sensors that mechanically
change resistance to deliver
variable voltage signals. Analog
signals are produced by variable
resistance type sensors and
voltage producing type sensors
Types of Sensor Signals
Digital Signal
• Digital signals are On – Off voltage
pulses, typically 2.5, 5.0 or 12
• AC voltage generating sensor
signals are converted into digital
signals. This conversion process
takes place by an Analog / Digital
Types of Sensors
• Hall Effect – Monitors the speed of a rotating
• Permanent Magnet – Monitors the speed of a
rotating component
• Pressure – Monitors pressure within a
component or system.
• Position – Monitors the position of a component.
• Thermistors – Measure temperature within a
component or system
Hall Effect Sensors
• Are frequently used where accuracy and fast response
are important
• Contain a powerful magnet, as the magnet passes over
a dense portion of the trigger wheel the 5 volts is
pulled to ground (.3V) through a transistor in the
sensor, when the magnet passes over a notch in the
trigger wheel the 5 volts is restored.
Hall Effect Sensors
Types of Hall Effect Sensors
used on today’s automobiles
•Cam Position Sensors (CMP
•Crankshaft Position Sensors
(CKP Sensors)
5 Volts
0 Volts
Permanent Magnet Sensors
• Consists of a permanent magnet surrounded by a
winding of wire
• When a metallic (iron or steel) is passed extremely
close the magnet, the magnetic field is interrupted and
a small amount of AC voltage is induced into the
• The induced AC voltage amount varies by:
– Speed of interruption
– Distance between magnet and metallic object and
– Strength of magnet.
Permanent Magnet Sensors
Types of Permanent
Magnet sensors used on
today’s automobiles are:
Reluctor Wheel
attached to Crankshaft
Permanent Magnet
Surrounded with wire
Signal from fast interruption
of magnetic field
Signal from slow
interruption of magnetic
Permanent Magnet Sensor
•Cam Position Sensors (CMP
•Crankshaft Position Sensors
(CKP Sensors)
•Wheel Speed Sensors (WSS
•Vehicle Speed Sensors (VSS
•Transmission Input & Output
Speed Sensors
Pressure Sensors and Switches
• Atmospheric pressure is 14.7 PSI or 29.92 inHg @ sea
• Pressure sensors monitor the pressure differential
between atmospheric pressure and the pressure within
a component or system
• Pressure sensors also monitor barometric pressure
(atmospheric pressure)
• Pressure sensors are three wire sensors; a three wire
sensor has a reference voltage wire (vref) from the
PCM, a ground and a signal voltage wire
• Pressure Switches are typically a two-wire “on/off”
switch located in a location where fluid pressure
monitoring is critical
Pressure Sensors and Switches
Types of Pressure sensors used on today’s
automobiles are:
Manifold Absolute Pressure Sensor (MAP
Fuel Tank Pressure Sensor (FTP Sensor)
Barometric Pressure Sensor (Baro Sensor)
Delta Pressure Feedback EGR Sensor (DPFE
Intake Air Flow Sensors
• Two ways to measure intake airflow
– Speed Density
• Measures intake air flow by sensing changes in intake
manifold pressure using a pressure type sensor
– Mass Airflow
• Measures the volume, density and on some the
temperature of the incoming air using a vane type or
hot wire type sensor
Vane Air Flow Sensor
• Utilizes an air flow door (flap) connected to a
Flap – Type or Vain Air Flow Meter
Hot Wire Air Flow Sensor
• The most common type of Mass Airflow
Sensor (MAF)
• All hot wire type sensors use the same
operating principle
Hot Wire Air Flow Sensor
• Incorporates a
small orifice inside
the main body, as
air passes through
the MAF a steady
flow also passes
through a small
• Inside there are
two wires, a
compensating wire
and a sensing wire.
Hot Wire Air Flow Sensor
Compensating Wire
• The compensating wire is a thermistor that
has a small amount of current passing through
• As the volume of air increases “cooling the
thermistor” the resistance (Voltage) of the
thermistor increases.
• The voltage represents the temperature of
incoming air.
Hot Wire Air Flow Sensor Sensing
• The sensing wire is maintained at a constant
temperature, approx 170° to 212°F
(depending on manufacturer) above the
temperature of the compensating wire
• This temperature is maintained by varying the
current flowing through it
Hot Wire Air Flow Sensor
• As air flow increases, current increases
• As air flow decreases, current decreases
• The amount of current flow = amount of air flow
Air = Amps
Position Sensors
• Provide linear or angular measurement in
relation to the position of that specific item or
component . There are two types of position
measuring sensors they are:
– Rheostat
– Potentiometer
• Is a two wire sensor
• Most common uses
of the rheostat is for
the Fuel Level
• Most common type of position sensor
• Contains a mechanical arm that is attached a
moving component (throttle plate, accelerator
pedal, airflow door, etc.) which causes it to
slide across a fixed resistor within the sensor
• The potentiometer
functions as a voltage
• Thermal resistors are used for sensing
• Two basic types of thermistors:
– Positive Thermal Coefficient (PTC)
– Negative Thermal Coefficient (NTC)
• Most common type used for sensing air temperature
and fluid temperatures
Positive Thermal Coefficient (PTC)
• Temperature and resistance (Voltage) are
directly proportional
Negative Thermal Coefficient (NTC)
• Temperature and resistance (Voltage) are
inversely proportional
Oxygen Detecting Sensors
• Located in the exhaust stream and provides
feedback information to the PCM about the
oxygen content in the exhaust
• Generates its own voltage signal
• There are three types of oxygen sensors
– Zirconium
– Titania
– Air Fuel Ratio
Oxygen Sensor Construction
• Has a center element
made of a ceramic
material called zirconium
• Two platinum electrodes
make up the inner and
outer surfaces of the
center element
• Internal temperature
must be kept above
O2S Voltage Generation
• O2 sensor operation
Air Fuel Ratio Sensors
• They perform the same function as zirconium
O2 sensors with some added benefits
– Allow a more accurate fuel control over a much
wider range (10.1 – 20.1 A/F Ratio)
– Operational within 10 seconds from a cold start,
thereby reducing cold start emissions.
– Inform the PCM exactly how rich or lean the A/F
ratio is
A/F Sensor Construction
Exhaust Guard
Ceramic Seal Assembly
Sensor Housing
Ceramic Support Tube
Planar Sensor Element
Protective Cap
Sensor Wires
Planar Sensor Element
• The air fuel ratio sensor
contain two zirconium O2
sensors, one to measure the
oxygen content of the
exhaust (zirconium Sense
Cell) and another zirconium
O2 sensor (zirconium pump
cell) to control the zirconium
sense cell. Also contains a
heater element.
Planar Sensor Element
• The PCM monitors the exhaust in the exhaust sense
chamber, using the zirconium sense cell. (High or Low
oxygen content)
• The PCM will either add or remove oxygen atoms to or
from the exhaust sense chamber to keep the sense cell
at lambda of 1 (14.7.1). This is accomplished by
reversing the polarity of the voltage to the zirconium
pump cell.
– Higher than 450mv – Oxygen is added
– Lower than 450mv – Oxygen is removed
• The amount of oxygen added or removed informs the
PCM exactly how rich or lean the A/F ratio is.
Piezoelectric Sensors
• The knock sensor is a piezoelectric sensor
• Detects vibrations arising from combustion knock
caused by low octane fuel, high engine
temperatures, detonation and or pinging
• Allows the PCM to control ignition timing for the best
possible performance while protecting it from
potentially damaging detonation
Outputs / Actuators
Operating Parameters Sensed
MAF Sensor
MAP Sensor
ECT Sensor
IAT Sensor
CKP Sensor
CMP Sensors 1 and 2
TP Sensors 1 and 2
APP Sensors 1 and 2
EGR Valve Position Sensor
Knock Sensor
HO2S 1/1, 2/1 and ½
PSP Switch
BPP Switch
AC On/Off Request
AC Pressure Sensor
Fuel Level Sensor
Fuel Tank (EVAP) Sensor
VSS Sensor
Trans Fluid Temperature Sensor
Turbine Speed Sensor
Trans Range Switch
Output Components Controlled
Fan Control Relay
Fuel Pump Relay
AC Clutch Relay
Throttle Actuator Control Motor
Malfunction Indicator Lamp
Camshaft Position Solenoids
EGR Valve
Fuel Injectors
Ignition Coils
Generator Field
EVAP Canister Purge Solenoid
EVAP Canister Vent Solenoid
Torque Converter Clutch Solenoid
Trans Pressure Control Solenoid
Trans Shift Solenoid
Types of Outputs/Actuators
• Actuators are devices that perform work, such
– Motors
– Stepper Motors
– Relays
– Solenoids
– Coils
– Lamps
Output Controls
• These devices are controlled by the PCM simply by
turning them “On” and “Off”, often by providing and
removing ground
Output Controls
• There are several types of output signals from
the PCM to control actuators; they are:
– Frequency
– Simple ON and Off switch type signal
– Duty Cycle type signal
– Pulse Width Modulated type signal
• Frequency is a measurement of how many times a
pattern repeats itself in one second
• Measured in Hertz (Hz)
• Frequency is measured from the beginning of a pattern
to the beginning of the next
Simple Off and On
• Actuator is either completely turned on or off
Duty Cycle
• Duty Cycle is the measurement of time an
actuator is turned on versus the amount of
time it is turned off
• Measured in Percentage (%)
Duty Cycle
• The measurement of duty cycle is the amount of
frequency divided by the “On Time”. Using the example
below; the frequency is 12.5Hz, the amount of time the
lamp is “On” 50.0Hz (12.5Hz ÷ 50.0Hz = 25% Duty
Pulse Width Modulation
• Pulse refers to turning an actuator on and off
• Width refers to the amount of time the actuator is
• Modulation refers to the fact that the actuator is
being controlled, or modulated, over a period of time
• Pulse Width Modulation (PWM) is different from
Duty Cycle in that both frequency and On time
varies. Duty Cycle signal frequency never changes
Pulse Width Modulation
• Example, the Fuel Injector is turned on once per engine
cycle, however as the engine RPM’s increase so does the
frequency of turning the injector on and off. In the
following illustration, the injector is turned on for 6.85ms
and 146 times in one second (146.1Hz)
Actuators (Load Devices)
• Most actuators rely on the principles of
• Relays, Fuel Injectors, Solenoids, and Motors
are examples of actuators that utilize
electromagnetism for their operation
• Most DC (Direct Current) motors contain four
main electrical components
– Commutator
• Consists of two electrical contacts that are connected to the
windings of the armature
– Brushes (Contacts)
• Brushes are mounted in a position that allows contact with
the commutator and are the means by which the
electromagnet receives voltage
– Armature
• Consists of the electromagnet and a shaft on which the
electromagnet is mounted. It is also referred to as a rotor
– Permanent Magnet
Stepper Motor
• A stepper motor functions similar to a DC motor,
however the stepper motor is much more precise in
its movement
• Common type of stepper motor is the Idle Air Control
Valve (IAC)
• A relay is an
device that utilizes a
small amount of
current to energize an
electromagnet that
closes the contacts in
a circuit carrying a
higher amount of
• Solenoids are used to control the
mechanical operation of a component, or
act as a valve to control gas or fluid flow
Electronic Exhaust
Fuel Injectors
Gas Recirculation
Valve (EGR)
Pressure Control
Ignition Coils
• The Coil is
part of both
the primary
• A lamp contains a resistor
called a filament that
emits light when current
flowing through it
• The other type of lamp
source is the LED (Light
Emitting Diode), LED is a
semiconductor light
source that is mainly
used as indicators, and in
the automobile the MIL
(Malfunction Indicator
OBD II General Diagnostic
OBD II General Diagnostic
• The following are eight steps to follow as a
suggested Diagnostic Strategy:
Verify the customer’s concern
Check the basics
Check for diagnostic trouble codes
Check and record freeze frame data
Check PID Data and Monitor Status
Review Repair History and TSBs
Perform Repairs
Verify Repairs
Verify The Customer’s Concern
– Obtain as much information as possible from the
When did it start to occur?
When does the condition occur?
Where does the condition occur?
How long does the condition last?
How often does the condition occur?
Have any repairs been done recently?
Are there aftermarket accessories on the vehicle?
– Establish a Baseline of the vehicle’s conditions,
symptoms, and abnormal operation
Check The Basics
– Mechanical systems, engine, transmission,
induction, exhaust and ignition systems, vacuum
lines/hoses, fluid levels and condition, etc.
– Battery, Starting, and Charging circuits for proper
operation, voltages, and voltage drops
– Sensors & actuators, and computer grounds
– Steady and reliable reference voltage at all sensors
– Unplug suspect sensors with KOEO, and look for
related PID values to change
– Compare possible PCM-default calculated values
to actual sensor voltage values
Review Repair History and TSBs
– Check for related TSBs for Service Procedure
updates, as well as possible computer
– Use other sources for specific service
information either in print or electronically
– Keep accurate repair-related records
• Diagnostics sequence
• Record trouble codes
Diagnostic Trouble Codes
– Check for pending codes that may indicate a
developing problem
– Check for codes stored in memory, even though
the MIL may be OFF
– Check the exact definition of each code
– Check the enabling criteria needed to run the
monitor and set the code
Freeze Frame
– Look at the data and make an accurate record of the exact data that is
– The data may not always send you to the exact problem, but it can
send you to the area of the problem
• Example #1: P0300
• Example #2: If a P0402 excessive EGR flow code is stored, the vehicle
runs OK, and Freeze Frame looks normal, check the EGR system. “Good”
Freeze Frame data is just as valuable as “Bad” data. The OBD II system
sensed a problem, but a component in the system may not be “out of
range” enough to set a specific DTC.
• Example #3: If a P03XX specific cylinder(s) misfire code that was stored
under a high load and low RPM condition, and Fuel Trim looks good,
check the ignition system. These conditions may indicate a rapid throttle
opening during a loaded acceleration from a standing stop or low vehicle
speed—exact conditions when ignition-related misfires occur.
Example #1
•A P0300 misfire code is stored
•LTFT is over +30%
•Engine is misfiring (lean)
•System is trying to add fuel
•Check fuel pressure
•Possible causes
•Restricted fuel filter
•Weak fuel pump
•Clogged injectors, etc.
•Vacuum Leak
Example #2
•A P0402 excessive EGR flow code is
•Vehicle runs OK
•Freeze Frame looks normal
•Check the EGR system.
•“Good” Freeze Frame data is just as
valuable as “Bad” data.
•The OBD II system sensed a problem,
but no component in the system was
“out of range” enough to set a DTC
Example #3
•A P03XX specific cylinder(s) misfire
code that was stored
• Under a high load at low RPM
•Fuel Trim is normal
•Check the ignition system
These conditions indicate a rapid throttle
opening during a loaded acceleration from a
standing stop or low vehicle speed—exact
conditions when ignition-related misfires occur.
PID Data and Monitor Status
• Select the inputs & outputs to be monitored. Too many
PIDs slows the update rate of the scan tool.
• Take a “Snapshot” of the data while the engine is running
or while driving the vehicle.
• Look carefully at the inputs & outputs and their values.
• Evaluate the information and compare PIDs one to
– Do MAP and BARO agree with the Key On Engine Off (KOEO),
and are they logical when the engine is running?
– Are IAT and ECT the same when the engine is cold and KOEO?
IAT / ECT Comparison
Set your scanner up for
PID comparison
• Engine Cold for
accurate test results.
• Compare Coolant Temp
with Intake Air Temp.
• ECT and IAT should be
within manufacturer’s
PID Data and Monitor Status
– Check battery voltage at KOEO and KOER
– Are IAC counts normal?
– Review “Snapshot” data for unusual trends
– Establish a Baseline of the vehicle
• Freeze Frame and Monitor Status establish a
“Before” picture of the vehicle to compare
“After” any repairs
• Keep your information simple but effective—
Concentrate on critical PIDs
Perform Repairs
• Use the information gathered from the
first six steps to assist you with your
final diagnosis and repair
• Use the appropriate tools and
equipment that are available to today’s
technician to diagnose and repair the
modern OBD II vehicle
Verify Repairs
• Drive the vehicle until the specific monitor(s) run to
• Running the monitor(s) allows the system(s) to test
• Once the monitor(s) run to completion, you can either
use Mode $06 Data and/or check for current or
pending DTCs to assist in verifying your repair(s)
If the customer drives the vehicle to run the monitor(s), make
them aware they are performing the drive cycle.
Make them aware that the OBD II system is designed to test
itself as they drive.
OBD II and Fuel Trim
Fuel Trim
• The fuel trim values are very important, so they are included in
Freeze Frame data.
• The data is shown as a percentage, either positive or negative,
with 0% being neutral.
• Greater than 0% means that the system is adding fuel, while
less than 0% means that the system is subtracting fuel.
Fuel Trim
• One of the most basic fuel
system diagnostic
procedures is to determine
if the engine control system
is operating in open or
closed loop.
• Whatever the HO2S sensor
does, the fuel trim corrects.
• For example, if the HO2S is
sensing a lean condition, the
STFT will begin to add fuel.
As the STFT adds fuel, the
LTFT will add fuel in order to
lower the STFT.
Fuel Trim
• The STFT values are volatile, meaning they are erased every time
the ignition key is switched off.
• The LTFT values are a ‘long-term adaptive’ strategy, which means
that it changes based off of STFT, and will adjust to changes
based off of all operating conditions over a period of time, such
as wear and tear on the engine and its subsystems
Fuel Trim
• As the PCM determines that STFT and LTFT are at their
maximum values and an air-to-fuel ratio imbalance
exists (such as a vacuum leak or leaking injector), it will
store a fuel trim related DTC.
• After establishing the loop status of the vehicle,
evaluate the scan tool data, along with a five-gas
analyzer, to determine if the PCM is providing a rich or
lean correction, and the extent of any such correction.
OBD II Scan Tools
Scan Tool
• Data transmitted to the scan tool (PIDs) from the
PCM include both digital and analog parameters.
• Digital parameters are often called ‘switch signals’,
and are either on or off, low or high, or yes or no.
• Analog parameters are often called ‘modified
signals’, and are values within a specific minimum-tomaximum range
Scan Tool
• Voltage readings, speed signals, and temperature
readings are just a few examples of PID data.
• All PIDs transmitted from the PCM to the scan tool
has a specific value or signal range described in
vehicle specifications.
• Knowledge of these PIDs specifications is needed
during comparison to the scan tool readings to
identify a system fault.
Scan Tool
• Scan tool readings that identify an open or a short
circuit are among the easiest to recognize.
• For example, if a resistive sensor is displayed on a
scan tool at or near the 5-volt reference voltage, the
sensor circuit to the PCM may be open.
• If, however, the displayed value is at or near 0-volts,
the circuit may be grounded
Scan Tool
• The PCM receives an analog or digital voltages from
the input sensors.
• The PCM processes these signals, and sends a
voltage signal or ground to output actuators.
• The scan tool displays these values (PID).
• Sometimes the scan tool displays a substitute value
to compensate for a failed sensor.
Scan Tool
• The substitute or default value is based on preprogrammed OEM engineering software.
• A sensor failure may cause the PCM to ignore the
signal from the failed sensor and operate on
‘substitute’ values stored in its memory.
• The PCM may transmit the ‘substitute’ values to the
scan tool in place of the failed sensor signal.
The technician is responsible for determining if substitution is displayed.
Scan Tool
• For general powertrain control diagnosis, the
following data parameters are among the
most important:
– System Voltage
– Engine Speed
– Engine Load
– Vehicle Speed
– Temperature
– Pressure
Generic OBD II Software
• Standardized scan tool modes of operation are
• Generic OBD II Software requires selecting
Generic or Global OBD II from the scan tool
Generic OBD II Software
• Standardized OBDII modes allow ‘generic’ scan tools to access the
same subset of information from all cars
– Mode $01: Current parameter data (PIDs)
– Mode $02: Freeze Frame data
– Mode $03: ‘Confirmed’ emission-related DTCs
• DTCs that are (or recently were) commanding the MIL on
– Mode $04: Clear DTCs and reset emission-related diagnostic
– Mode $05: HO2S monitoring test results
– Mode $06: Test results for non-continuously monitored systems
– Mode $07: ‘Pending’ emission-related DTCs
– Mode $08: Bi-directional controls (never required/implemented for
generic OBD)
– Mode $09: Vehicle data (VIN, Calibration ID, etc.)
– Mode $0A: ‘Permanent’ emission-related DTCs
• Stored when MIL commanded on
• Cannot be erased by scan tool
• Only erased by OBD system itself once monitor runs and passes
OEM Enhanced OBD II Software
• Enhanced scan tools include additional diagnostic
• These capabilities include non-standardized and
non-emission related information not available in
the Generic OBD II Software.
Manufacturer specific DTCs
Manufacturer specific PIDs
Enhanced “Snapshot” functions
Bi-directional controls
OEM Enhanced OBD II Software
• It is advantageous to use both the Generic and
Enhanced protocols.
– More data
– Bi-directional controls
– Identifying substituted values, etc.
OEM Specific OBD II Software
Manufacturer Specific Scan Tools/Software
• Performs OBD II related functions and interfaces with
other vehicle computers.
• Most vehicles today has a multiplexed vehicle
network system.
• Reprogramming functions.
• Increased number of PID and DTC data, descriptions,
diagnostic tips, and strategies.
• Up-to-date technical support and upgrades directly
from the vehicle manufacturer.
OBD II 16-pin Connector
Pin #1: Discretionary to Vehicle Manufacturers
Pin #2: SAE J1850 Protocol “Hi Signal” [Data (+)]
Pin #3: Discretionary to Vehicle Manufacturers
Pin #4: Chassis Ground (Typically B-)
Pin #5: Sensor Ground (Typically B-)
Pin #6: ISO 15765 CAN “Hi Signal” [Data (+)]
Pin #7: ISO 9141-2 and 14230 Protocol “K-Line”
Pin #8: Discretionary to Vehicle Manufacturers
OBD II 16-pin Connector
Pin #9: Discretionary to Vehicle Manufacturers
Pin #10: SAE J1850 Protocol “Lo Signal” [Data (-)]
Pin #11: Discretionary to Vehicle Manufacturers
Pin #12: Discretionary to Vehicle Manufacturers
Pin #13: Discretionary to Vehicle Manufacturers
Pin #14: ISO 15765 CAN “Lo Signal” [Data (-)]
Pin #15: ISO 9141-2 and 14230 Protocol “L-Line”
Pin #16: Unswitched B+
ASE L1 Composite Vehicle scan tool
• In this example
there are 63 PIDs
listed with
Min/Max values
for each data
parameter listed
OBD II Monitors
Mode $06
• Monitors are self tests of emission components or
Comprehensive Component
Fuel Trim
O2 Sensor
O2 Heater
Catalytic Converter
Air Injection Systems
• Three or more incomplete monitors will
cause a vehicle to fail smog inspection for
1996 to 2000 model year vehicles and 2 or
more on 2001 and newer vehicles.
• Monitors are designed to run to completion
during normal vehicle operation.
– Enabling criteria must be met for monitors to
– Enabling criteria for each monitor is different.
• Drive cycle would include enabling criteria
for all monitors to run.
Mode $06 Data
• Mode $06 displays test results for noncontinuous monitors.
• Mode $06 can give the results of a two trip
monitor in one trip.
• Can confirm a successful repair after one trip.
• Test results can indicate if a monitored system
is close to failing.
Terms Used in Mode $06 Data
• TID = Test Identification – The system being tested (MIDs = Monitor
Identification in CAN systems)
• CID = Component Identification – The component of the system
being tested.
• TLT = Test Limit – To pass a test, a test value must be either a
minimum or maximum value ( or between a min/max value)
• Hexadecimal ($) = Numeric/Alpha unit that indicates a specific
TID/CID or test value (Example: $02)
• Raw Data = Numeric data indicating the actual test results.
• Manufacturer’s Conversion Factor = Used to convert test data to
values that can be used to diagnose a system (volts, Ohms, amps,
inches of mercury, etc.).
• Test Value = Actual test results.
• Results = Indicates whether system/component either passed or
failed a test.
• Limit Type = Test pass/fail limits
Mode $06 Data
**Non-Cont. Monitoring Test Result**
ECU ID: $10 Test ID: $02 Component: $02
Min: 12344 Max: 32768
Value: 11211
Results: Fail
• This scan tool shows the actual test results of
the monitor
• Note the minimum and maximum parameters
Mode $06 Data
• A vehicle failed for a P0420 (CAT efficiency
below threshold)
• A new CAT was installed and codes cleared.
• Check the enabling criteria to run the CAT
monitor and run that drive cycle.
Vehicle failures due to
monitors not run to
Mode $06 Data
• Vehicle fails an ASM test for monitors not run.
• Smog technician advises vehicle owner to drive the vehicle
for 50 miles.
• Vehicle owner returns two days later with the same results
of monitors not running.
• A diagnosis has been authorized.
• Diagnosis has been made and no problems found. Vehicle
now referred to Referee.
Mode $06 Data
•Mode $06 shows TID $02 CID $60 has failed. (EVAP weak vacuum
test 1)
•Possible reason EVAP Monitor has not run
Mode $06 Data
• TID $07 CID $4D shows EGR passed at maximum
Mode $06 Data
• Code P0404 found in pending (Control Circuit)
Mode $06 Data
• Vehicle is at Operating temperature
• Note ECT input is low at 111 degrees
• Note fuel trims at negative -32.8
Mode $06 Data
• Testing the EGR circuit
• Found a voltage drop of 1.57 volts on the ground side
• Cause of pending code P0404
Mode $06 Data
•Testing the ECT circuit
•Found 2.24 voltage drop on the ground side causing a higher
voltage signal to PCM.
•ECT sensor itself is within manufacture specs.
•Causing Injector pulse width to increase.
Mode $06 Data
• The ECT and EGR harnesses have been
repaired, and the codes and monitors reset. A
drive cycle has been completed and all the
monitors have run to completion. Vehicle now
passes a smog check and vehicle owner
feedback states vehicle is getting better fuel
2011 BAR Update Course
Catalytic Converter Testing
• The purpose of the catalytic converter
• The fundamental needs for proper catalytic converter operation
• Catalytic converter replacement requirements – CARB Installer’s List
• Causes of catalytic converter failures
• Pre-OBDII catalytic converter testing
• OBDII catalytic converter testing
The Catalyst
Catalysts are needed to reduce emissions to acceptable levels without
dramatically reducing performance and fuel economy. This is true of
HC, CO and NOx, but NOx is the emission that is most dependent on
the catalyst for emissions compliance
There are two types of catalysts:
•Reduction catalysts cause NOx to be reduced into O2 and N2.
•Oxidation catalysts cause HC and CO to oxidize with any available
oxygen into CO2 + H2O.
*Unfortunately, oxidation will only occur when there is enough free
oxygen, and reduction is very hard to achieve with the high oxygen
levels that occur in lean burn operation.
The Catalyst
A catalyst can not clean up CO and HC unless there is enough oxygen
in the exhaust.
Many catalysts can not clean up NOx unless the level of oxygen in the
exhaust is very low.
There is no fuel mixture that allows CO, HC and NOx to all be catalyzed
at maximum efficiency.
Gasoline Direct Injection (GDI) engines and Homogeneous Charge
Compression Ignition (HCCI) engines operate under lean burn
conditions frequently. Hybrid electric vehicles often operate their internal
combustion engines for shorter periods of time that would prevent
traditional catalytic converters from reaching operational temperatures.
The Catalyst
Many late model cars depend heavily on the catalyst to reduce NOx at
extremely high levels (95+%). This simply is not possible unless the
oxygen level is low enough. If carbon deposits or other problems
increase the exhaust oxygen level, a perfectly good catalyst will
operate at reduced efficiency.
Some late model cars depend on the catalyst to clean up over 99.3% of
their NOx emissions.
This will only occur if the exhaust oxygen level is very low.
Many minor problems can increase exhaust oxygen levels and inhibit
catalyst efficiency.
Catalyst Approval Criteria
As of January 1, 2009, CARB approval/exemption requirements for all
aftermarket replacement catalytic converters changed.
These changes increased performance requirements and improved
identification labels. As a result, aftermarket converters now come
closer to the original equipment converters in both performance and
Catalytic Converter Replacement
Technicians and vehicle owners do NOT have the option of replacing
original equipment catalytic converters without first meeting the
requirements of the CARB Installers Checklist for New Aftermarket
Catalytic Converters, as applicable1. The vehicle model is specifically included in the application list for
the catalytic converter model I intend to install, and the converter
model is approved for use in California.
2. I have verified that the vehicle manufacturer’s warranty for the
stock catalytic converter has expired. Warranties will range from
a minimum 7 years/70,000 miles to 15 years/150,000 miles.
3. I have confirmed the need for a replacement catalytic converter. If
the stock converter is still installed, a diagnosis that it is
malfunctioning is required.
Catalytic Converter Replacement
4. The replacement converter will be installed in the same location as the
stock converter (the front face location will be within three inches
compared to the stock design).
All oxygen sensors will remain installed in their stock location(s).
6. The catalytic converter will be installed on a “one for one basis (only
one OEM converter is being replaced by the converter to be installed).
Decreasing or increasing the number of catalytic converters (compared
to the stock configuration) is prohibited.
7. Warranty Card- I have:
(a) Filled out the warranty card
(b) Obtained the customer’s signature an the card
(c) Attached the card to the original repair order
(d) Returned a copy of the warranty card to the catalytic converter
8. I have filed and will maintain a copy of all documentation for a period of
at least four years from the date of installation.
Catalytic Converter Replacement
Installers shall keep documentation regarding the installation of the
new catalytic converter including all of the above information. This
documentation shall be made available to CARB or it’s
representative as provided for in title 13, section 222(b)(8). All such
records shall be maintained for four years from the date of sale of
the catalytic converter.
What Can Damage A New
Quality catalytic converters can perform well for hundreds of
thousands of miles
•Anything that significantly increases the amount of HC and/or CO that
is oxidized in the converter will increase the operating temperature of
the catalyst
•Failing to use manufacturer approved engine oil
•Coolant seeping into the combustion chamber or exhaust
What Can Damage A New
If any of the following conditions exist, the customer (or referring shop)
should be notified that the engine might have existing faults that could
damage the new converter:
•CO in excess of 2.0% (pre-catalyst)
•HC in excess of 400 ppm (pre-catalyst)
•Indications of high oil consumption
•Indications of combustion/coolant leaks
•Indications of O2 sensor faults
•Indications of modifications or poor maintenance
Pre OBDII Catalytic Converter
Catalytic Converter Cranking
There is typically no CO2 present in the atmosphere. CO2 is a product
of combustion. Therefore any carbon dioxide emissions measured
during typical starter draw test, with ignition disabled must be created
in the catalytic converter.
A good catalytic converter should be capable of converting the
Hydrocarbon fuel (HC) that is pumped through the engine during the
starter test to 13% carbon dioxide.
In order to create 13% CO2 during a starter draw test the following
must occur:
•The catalytic converter must be completely warmed up.
•Fuel delivery must be functioning normally. *The CO2 is being created
by converting the fuel that is being pumped through the engine.
•Ignition must be completely disabled.
Catalytic Converter Cranking
1. Start the engine and drive the car to insure that it is warmed up
2. Run the engine at 2000 rpm to insure that the catalytic converter is
3. Turn off the ignition or hit the analyzer kill switch.
4. IMMEDIATELY after the engine stops, disable the ignition (ground
the coil secondary or disconnect the coil primary) and crank the
engine over while watching the CO2 levels on the exhaust analyzer.
NOTE: The fuel system must remain functional! Do not disable
rpm sensor or engage clear flood mode! Disable the ignition
system only! Do not allow the converter to cool down!
Catalytic Converter Cranking
5. The CO2 level should reach and maintain 13% in about 10 seconds.
If the CO2 level does not reach at least 13%, or the CO2 level only
spikes to 13%, the catalytic converter is weak.
If the CO2 level is below 13% make sure that there is sufficient HC and
O2 to make the CO2 from. If the CO2 level drops below 1% or HC drops
below 500 ppm the test will not be valid.
*This test is difficult to perform on many DIS cars since the
ignition is not easily disabled.
Use the snap throttle test on such cars.
Shop Practice
Catalytic Converter Snap Throttle
When the engine is running at a stoichiometric 14.7:1 fuel mixture
with no air injection there is very little oxygen in the exhaust. Cars
equipped with carburetors will have higher normal levels of oxygen
due to poorer fuel atomization and vaporization.
During a snap throttle test, CO will increase due to a suddenly rich
mixture on acceleration. CO will continue to increase until the O2
level begins to rise. During this snap acceleration all excess oxygen
will be used up by the catalytic converter to convert CO to CO2. As
the O2 level rises O2 will be used up by the catalytic converter to
convert CO to CO2 and the CO level will begin to drop as O2 rises. A
good catalytic converter will therefore prevent the O2 level from
exceeding 1.2% until the CO level begins to drop.
Catalytic Converter Snap Throttle
1. Drive the car until the engine and catalytic converter are fully
warmed up.
2. Disable the air injection system.
3. Run the engine at 2000 rpm and wait for stable exhaust readings
with O2 level no higher than 0.5%. Propane enrichment may be used
to reduce O2 level to 0.5%.
4. Snap and release the throttle.
5. Watch the CO emissions climb and note the oxygen level at the
instant the CO level peaks. Oxygen level at the instant that CO level
peaks should not exceed 1.2%.
Catalytic Converter Snap Throttle
Note: It is normal for Oxygen level to rise after CO has peaked.
If the O2 level exceeds 1.2% before the CO level peaks the catalytic
converter is weak.
This test works best on cars that have sequential fuel injection and DIS. The
cranking catalytic converter test tends to be difficult to perform on these
same cars.
Shop Practice
Catalytic Converter Invasive
Catalytic converter efficiency can be determined by sampling the
exhaust gas before and after the catalytic converter. Kits are available
from Thexton (No. 389), OTC and others to tap through single wall
exhaust pipes. Other pre-CAT sampling locations may include the
EGR port, EGO port and air injection ports. (EGO is not
recommended). Record both the before cat and tailpipe exhaust gas
with the engine well tuned, preconditioned, no exhaust leaks and no
air injection. Fuel mixture may have to be manipulated and/or misfires
induced to create the proper oxygen level for proper evaluation.
Catalytic Converter Invasive
(HC in) - (HC out)
----------------------- x 100 = CAT HC efficiency
(HC in)
HC oxidation efficiency should be 90% when O2 in exceeds 1% and O2
out exceeds 0.5% You may need to induce a misfire to create the
proper O2 levels.
(CO in) - (CO out)
----------------------- x 100 = CAT CO efficiency
(CO in)
CO oxidation efficiency should be 90% when O2 in exceeds 1% and O2
out exceeds 0.5%
Catalytic Converter Invasive
(NOx in) - (NOx out)
------------------------ x 100 = CAT NOx efficiency
(NOx in)
NOx reduction efficiency should be 90% when O2 in is less than
0.5%. This test may require loaded mode testing and/or disabling
EGR. It may also be necessary to artificially enrich the air-fuel
mixture to reduce O2 content below 0.5%.
Catalytic Converter Invasive
NOTE: EPA certifications only require catalysts to oxidize CO &
HC at 70% efficiency, and to reduce NOx at 60% efficiency. This
may not be sufficient to allow some cars to pass ASM tests. Some
cars may require 90% efficiency in NOx reduction. Others may be
fine with less than 50%.
The oxidation and reduction efficiency of good catalysts vary due to
oxygen levels in the exhaust system during normal running conditions
of those cars. 2-way catalysts operating with high oxygen levels in the
feed-gas should meet the above standards for CO and HC oxidation.
All 3-way catalysts operating with low oxygen levels in the feed-gas
should meet the above standards for CO & HC oxidation and NOx
Shop Practice
Catalytic Converter Light Off
This test must be performed with the engine cold.
Start the cold engine and monitor exhaust gas at 2500 rpm during
warm up.
Exhaust emission readings should be relatively stable except during
the following three events:
1. Initial start up & stabilization.
2. Initialization of closed loop.
3. Catalytic converter “light-off”.
This can be graphed or “traced” so that the readings before and after
converter light off can be compared. Use the same formula shown in
the “Invasive Test”.
Shop Practice
Catalytic Converter Misfire Test
When a misfire occurs the catalytic converter releases a tremendous
amount of heat as it oxidizes the unburned HC into H2O and CO2. The
increased temperature that this causes increases the Catalyst
efficiency. This reaction allows us to test the catalyst by inducing a
1. Allow the car to run for several minutes at 2500 rpm after it is
properly warmed up.
2. Disable one spark plug. Do NOT allow the engine or exhaust
system to cool down as you do this. It is permissible to turn the
engine off while disabling the spark plug, but this must be done and
the engine restarted within three minutes. Some engine analyzers will
allow you to kill an individual cylinder without turning the engine off.
Catalytic Converter Misfire Test
3. As you induce the misfire, the HC will increase dramatically for several
seconds. Then, as the catalyst heats up, the HC level should drop off
significantly. Record the Peak HC level and the level that HC drops to as
it gets hot.
A good catalytic converter will be able to reduce the HC emissions to
about 50% or less of the peak HC emissions in just a few seconds.
This test must be performed with caution. Do NOT perform this test
for extended periods or under a load. A catalytic converter can
overheat to the point of melt-down in as little as 12 seconds if
multiple spark plugs are disabled while under load. Do not disable
multiple cylinders and do not perform the test under loaded
Shop Practice
Catalytic Converter Temperature
and 4-Gas Test
Completely warm up the engine and exhaust system. Run the following
test using a 4 or 5 gas analyzer and an infrared temperature sensing
The accuracy of infrared temperature sensing varies according to the
"emissivity" of the surface being sensed. Sometimes it is helpful to
paint the surfaces with a quick drying flat black paint before testing.
Painting is recommended if the two surfaces have different surface
Is there
more than
The test will not be accurate. There is not
enough oxygen for the CAT to do it’s job.
Is there
more than
0.4% CO?
Is there
more than
100 ppm
There is not enough fuel present
for the CAT to oxidize.
Is there
less than
13% CO2?
Repair engine or exhaust system and/or
disable the air injection system.
Repair engine
systems and retest.
Repair engine
systems and retest.
Is there
more than
400 ppm
Is there
more than
2.0% CO?
Is there a 200
temperature gain
in the CAT?
Replace the
Repair engine
systems and retest.
Shop Practice
OBDII Catalytic Converter
OBDII Catalytic Converter
A properly operating catalytic converter uses oxygen to oxidize HC
and CO into CO2 and O2. The process changes the oxygen level in
the exhaust. Under tightly controlled conditions, the PCM will initiate
a pattern of fuel control commands and monitor the oxygen sensor
response. In order to pass the monitor test the oxygen sensor
response must fall within a pre-determined pattern. The pattern is
different for each car but the rear oxygen sensor is often compared to
the front oxygen sensor to identify changes that the catalytic
converter causes in exhaust oxygen content.
Catalytic Converter OBDII Monitor
The OBDII monitor test is typically run automatically on every trip in
which the required enable criteria are met. The enable criteria are
different on each vehicle. Details of the enable criteria and the drive
cycle required to meet those criteria can be found in published
service manuals.
As mentioned elsewhere in this document, many vehicles that use
“exponentially weighted moving averages” as part of the OBDII
catalyst monitoring have reduced accuracy immediately after the
memory has been cleared. Under these temporary conditions, false
fails and false passes are more likely to occur. With this possible
exception, OBDII monitors are very accurate. If in doubt, clear codes
and retest.
OBDII Catalytic Converter Test
Check List
• Confirmation of baseline gas data
• Confirmation of proper engine mechanical operation
• Confirmation of proper ignition system operation
• Confirmation of proper fuel system operation
• Check for Closed Loop Fuel Control
OBDII Catalytic Converter Test
Check List
• Check data stream for fuel trim
• Check readiness monitors
• Check for pending codes
• Check for unrelated codes
• Check Exhaust system for leaks
 Visual
 Audible
 Pressure Test
Smoke Test the Exhaust System for Leaks
OBDII Catalytic Converter Test
Check List
• Secondary Oxygen Sensor Testing
Graphing Meter
Volt Meter
Scan Tool
• Locating Specifications
Manufacturer Documentation
Other service information providers
Related fault code flow charts
Mode 6 data parameters
Scenario #1
On an OBDII equipped vehicle
All test results are ok to this point, but NOx is still too high
What test(s) should be performed?
Invasive Test with calculations
What is the expected Oxygen Sensor results?
Light-Off Test with calculations
What is the expected Oxygen Sensor results?
Shop Practice
BAR wishes to thank the following individuals for
their contributions
Northern Group,
Catalytic Converter Testing
Southern Group,
Christine Vinson
Dennis Shortino
Justin Bunch
Kevin McCartney
Kurt Shadbolt
Larry Williams
Michael Sherburne
Ray Ortiz
Jay Hartley
Jonathan Summers
Jose Vallejo
Mark Ellison
Michael Garibay
Steven Tomory

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