Drive cycle ISUZU AXIOM 2002 Service Repair Manual

1A±24
HEATING, VENTILATION AND AIR CONDITIONING (HVAC)
Diagnosis
Air Conditioning Cycle Diagnosis
ConditionPossible causeCorrection
No cooling or insufficient cooling.Magnetic clutch does not run.Refer to ªMagnetic Clutch Diagnosisº
in this section.
Compressor is not rotating properly.
Drive belt is loose or broken.Adjust the drive belt to the specified
tension or replace the drive belt.
Compressor is not rotating properly.
Magnetic clutch face is not clean and
slips.Clean the magnetic clutch face or
replace.
Compressor is not rotating properly.
Incorrect clearance between
magnetic drive plate and pulley.Adjust the clearance. Refer to
Compressor in this section.
Compressor is not rotating properly.
Compressor oil leaks from the shaft
seal or shell.Replace the compressor
Compressor is not rotating properly.
Compressor is seized.Replace the compressor
Insufficient or excessive charge of
refrigerant.Discharge and recover the
refrigerant. Recharge to the
specified amount.
Leaks in the refrigerant system.Check the refrigerant system for
leaks and repair as necessary.
Discharge and recover the
refrigerant. Recharge to the
specified amount.
Condenser is clogged or insufficient
radiation.Clean the condenser or replace as
necessary.
Temperature control link unit of the
heat unit is defective.Repair the link unit.
Unsteady operation due to a foreign
substance in the expansion valve.Replace the expansion valve.
Poor operation of the electronic
thermostat.Check the electronic thermostat and
replace as necessary.
Insufficient velocity of cooling air.Evaporator clogged or frosted.Check the evaporator core and
replace or clean the core.
Air leaking from the cooling unit or air
duct.Check the evaporator and duct
connection, then repair as
necessary.
Blower motor does not rotate
properly.Refer to Fan Control Lever (Fan
Switch) Diagnosis in this section.
*For the execution of the charging and discharging
operation in the table above, refer to
Recovery,
Recycling, Evacuating and Charging in this section.

DRIVE LINE CONTROL SYSTEM (TOD) 4B2±30
Checking Failed TOD Control Unit Pin
NOTE:
1. Unplug the ECU connector and the pins, unless
otherwise specified.
2. Before removing the ECU, turn off the ignition switch.
3. If the standard values are not observed, check the
pins with other testers.
Check
Pin
No.Circuit to be
testedIgnition
Switch
PositionEngine
StateUnit
Scale/
RangeMeasure
between
Pin No.Standard ValueNote
22P-GNDOFFSTOP
22, 47Continuity : OK
46GNDIOFFSTOP
46, 47Continuity : OK
47GND 2OFFSTOP
47, GNDContinuity : OK
314H SWOFFSTOP
31, 47No continuity
(high, 4L) : OK
444L SWOFFSTOP
44, 47No continuity
(high) and
continuity (4L) :
OK
42AXLE SWONRUN
42, 47Continuity(TOD,
4L) : OKRemove ECU connector and start
the engine. Move the vehicle forth
and back to connect axle surely.
29DIAGOFFSTOP
29 (TOD),
8 (DLC
Connec-
tor)Continuity : OKDLC connector terminal 8
7IND.AONSTOPDCV7 (+), 47
(±)8.0 ~14.5 Vwhen the indicator lamp is turned
off.
20CHECK
TODONSTOPDCV20 (+), 47
(±)8.0 ~14.5 VWhen the indicator lamp is turned
off.
33ABS INONSTOPDCV33 (+), 47
(±)6.0 ~11.0 V
12REFONSTOPDCV12 (+), 47
(±)5 ~9 VConnect ECU
32FRT.(+)ONSTOPDCV32 (+), 47
(±)0.7 ~6 VConnect ECU and move the
vehicle (off one tooth of speed
sensor ring) making sure of
voltage change.
45RR.(+)ONSTOPDCV45 (+), 47
(±)0.7 ~6 VConnect ECU and move the
vehicle (off one tooth of speed
sensor ring) making sure of
voltage change.
13COM(-)ONSTOPDCV13 (+), 47
(±)0VConnect ECU
14VIGONSTOPDCV14 (+), 47
(±)8 ~14.5 V
34VBOFFSTOPDCV34 (+), 47
(±)8.0 ~14.5 V
37BRAKE
SWOFFSTOPDCV37 (+), 47
(±)8 ~14.5 VPress brake pedal
15TPSONSTOPDCV15 (+), 47
(±)PWM duty cycle
10%(MAX) ± 90
%(MIN)Step on the accelerator pedal and
make sure that duty cycle
changes.

DRIVE LINE CONTROL SYSTEM (TOD) 4B2–111
Step Action Yes No
1 Are the brake and ABS systems healthy?
Go to
Step 2
Repair the brake
and ABS. (Refer to
section 5A and 5B)
2 Turn on the star ter switch.
Is the battery voltage observed between terminals 14 and 47?
Go to
Step 3
Repair the
battery system.
Go to
Step 5
3 1. Select the TOD switch to the 2H position.
Does the voltage between terminals 36 and 47 range between
7.5 and 16V (0.12 seconds make a cycle)? Go to
Step 4
The ECU has
failed. Replace
the ECU.
Go to
Step 5
4 1. Turn off the starter switch.
2. Disconnect the connector (C–37).
Is there the continuity between the connector terminal (C–37) 14
and (C–6) 8?The
phenomenon is
not reproduced.
Refer to
“Trouble
intermittently
observed".
Repair the
harness.
Go to Step 5
5 Check that all the par ts are mounted.
Is this step complete? Verify the repair. Go to
Step 5

5A±8BRAKE CONTROL SYSTEM
Pressure Increase (Re-apply)
The re-apply sequence is initiated to achieve optimum
braking. The isolation valve is momentarily opened to
allow master cylinder and pump pressure to reach the
brakes. This controlled pressure rise continues until the
wheel is at optimum brake output or until the brake
pressure is brought up to the master cylinder output
pressure.
If more pressure is required, more fluid is drawn from the
master cylinder and applied to the brakes. The driver may
feel slight pedal pulsations, or pedal drop, this is normal
and expected.As fluid is re-applied to the brakes, the wheel speed will
reduce. If the wheels approach imminent lockup again,
the module will isolate, dump and re-apply again. This
cycle occurs in millisecond intervals, allowing several
cycles to occur each second. It is a much faster and more
controlled way of ªpumping the pedalº.
C05RW014
Legend
(1) Brake
(2) Master Cylinder

6A±87
ENGINE MECHANICAL (6VE1 3.5L)
Main Data and Specification
General Specification
ItemSpecificationsItem6VE1
Engine type, number of cylinders and arrangementWater cooled, four cycle V6
Form of combustion chamberPent-roof type
Valve mechanism4-Cams, 4-Valves, DOHC Gear & Belt Drive
Cylinder liner typeCasted in cylinder drive
Total piston displacement3494 cc
Cylinder bore x stroke93.4mm x 85mm
(3.677 in x 3.346 in)
Compression ratio9.1
Compression pressure at 300rpm1.37 MPa (14.0 Kg/cm2)
Engine idling speed rpmNon adjustable (750)
Valve clearanceIntake: 0.28 mm (0.11 in)
Exhaust: 0.30mm (0.12in)
Oil capacity5.3 liters
Ignition timingNon adjustable (20
BTDC at idle rpm)
Spark plugPK16PR11, RC10PYP4, K16PR-P11
Plug gap1.0 mm±1.1 mm(0.0394 in ± 0.0433 in)

6E±1
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
AXIOM
ENGINE
6VE1 3.5L ENGINE
DRIVEABILITY AND EMISSIONS
CONTENTS
Specifications 6E±6. . . . . . . . . . . . . . . . . . . . . . . . . . .
Tightening Specifications 6E±6. . . . . . . . . . . . . . .
Diagrams and Schematics 6E±7. . . . . . . . . . . . . . . .
PCM Wiring Diagram (1 of 7) 6E±7. . . . . . . . . . . .
PCM Wiring Diagram (2 of 7) 6E±8. . . . . . . . . . . .
PCM Wiring Diagram (3 of 7) 6E±9. . . . . . . . . . . .
PCM Wiring Diagram (4 of 7) 6E±10. . . . . . . . . . . .
PCM Wiring Diagram (5 of 7) 6E±11. . . . . . . . . . . .
PCM Wiring Diagram (6 of 7) 6E±12. . . . . . . . . . . .
PCM Wiring Diagram (7 of 7) 6E±13. . . . . . . . . . . .
PCM Pinouts 6E±14. . . . . . . . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Blue Connector
± Row ªF1 ~ 20º 6E±14. . . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Blue Connector
± Row ªF20 ~ 40º 6E±15. . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Blue Connector
± Row ªF41 ~ 60º 6E±16. . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Blue Connector
± Row ªF61 ~ 80º 6E±17. . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Red Connector
± Row ªS1 ~ 20º 6E±19. . . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Red Connector
± Row ªS21 ~ 40º 6E±21. . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Red Connector
± Row ªS41 ~ 60º 6E±23. . . . . . . . . . . . . . . . . . . . .
PCM Pinout Table, 80-Way Red Connector
± Row ªS61 ~ 80º 6E±25. . . . . . . . . . . . . . . . . . . . .
Component Locators 6E±27. . . . . . . . . . . . . . . . . . .
Undercarriage Component Locator 6E±29. . . . . .
Fuse and Relay Panel (Underhood
Electrical Center) 6E±30. . . . . . . . . . . . . . . . . . . . .
Sensors and Miscellaneous Component
Locators 6E±31. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Diagnosis 6E±33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Strategy-Based Diagnostics 6E±33. . . . . . . . . . . . .
DTC Stored 6E±33. . . . . . . . . . . . . . . . . . . . . . . . . . .
No DTC 6E±33. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
No Matching Symptom 6E±33. . . . . . . . . . . . . . . . .
Intermittents 6E±33. . . . . . . . . . . . . . . . . . . . . . . . . .
No Trouble Found 6E±33. . . . . . . . . . . . . . . . . . . . .
Verifying Vehicle Repair 6E±33. . . . . . . . . . . . . . . .
General Service Information 6E±33. . . . . . . . . . . . . .
OBD II Serviceablity Issues 6E±33. . . . . . . . . . . . .
Emissions Control Information Label 6E±34. . . . .
Visual / Physical Engine Compartment
Inspection 6E±34. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Basic Knowledge of Tools Required 6E±35. . . . . .
Serial Data Communications 6E±35. . . . . . . . . . . . . . Class 2 Serial Data Communications 6E±35. . . . .
On-Board Diagnostic (OBD II) 6E±35. . . . . . . . . . . . .
On-Board Diagnostic Tests 6E±35. . . . . . . . . . . . .
Comprehensive Component Monitor
Diagnostic Operation 6E±35. . . . . . . . . . . . . . . . . .
System Status and Drive Cycle for
Satisfying Federal Inspection/Maintenance
(I/M 240) Regulations 6E±36. . . . . . . . . . . . . . . . . .
Common OBD II Terms 6E±36. . . . . . . . . . . . . . . . .
The Diagnostic Executive 6E±36. . . . . . . . . . . . . . .
DTC Types 6E±37. . . . . . . . . . . . . . . . . . . . . . . . . . .
Decimal/Binary/Hexadecimal Conversions 6E±39
Verifying Vehicle Repair 6E±39. . . . . . . . . . . . . . . .
Reading Diagnostic Trouble Codes Using
The Tech 2 Scan Tool 6E±39. . . . . . . . . . . . . . . . .
Tech 2 6E±40. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Tech 2 Features 6E±41. . . . . . . . . . . . . . . . . . . . . . .
Getting Started 6E±41. . . . . . . . . . . . . . . . . . . . . . . .
Operating Procedure (For Example) 6E±42. . . . .
DTC Modes 6E±43. . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC Information Mode 6E±43. . . . . . . . . . . . . . . . .
Miscellaneous Test 6E±44. . . . . . . . . . . . . . . . . . . .
Lamps Test 6E±44. . . . . . . . . . . . . . . . . . . . . . . . . . .
Relays Test 6E±46. . . . . . . . . . . . . . . . . . . . . . . . . . .
EVAP Test 6E±47. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel System Test 6E±48. . . . . . . . . . . . . . . . . . . . . .
Instruments Test 6E±50. . . . . . . . . . . . . . . . . . . . . . .
EGR Control Test 6E±52. . . . . . . . . . . . . . . . . . . . . .
Variable Intake Manifold Solenoid Test 6E±52. . .
Injector Balance Test 6E±54. . . . . . . . . . . . . . . . . . .
Plotting Snapshot Graph 6E±54. . . . . . . . . . . . . . . . .
Plotting Graph Flow Chart (Plotting graph
after obtaining vehicle information) 6E±55. . . . . .
Flow Chart for Snapshot Replay (Plotting
Graph) 6E±56. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Primary System-Based Diagnostic 6E±57. . . . . . . . .
Primary System-Based Diagnostic 6E±57. . . . . . .
Fuel Control Heated Oxygen Sensor 6E±57. . . . .
HO2S Heater 6E±57. . . . . . . . . . . . . . . . . . . . . . . . .
Catalyst Monitor Heated Oxygen Sensors
and Diagnostic Operation 6E±57. . . . . . . . . . . . . .
Misfire Monitor Diagnostic Operation 6E±58. . . . . . .
Misfire Monitor Diagnostic Operation 6E±58. . . . .
Misfire Counters 6E±58. . . . . . . . . . . . . . . . . . . . . . .

6E±16
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
PCM Pinout Table, 80-Way Blue Connector ± Row ªF41 ~ 60º
060RY00046
PINPIN FunctionWire ColorIGN ONENG RUNRefer To
F41Throttle Position(TP) 1
Sensor GroundGRN0.0V0.0VGeneral Description and
Operation, TPS
F42Fuel Pump RelayPNK/WHT0.0VB+On Vehicle Service, Fuel
Pump Relay
F43Adaptor CaseVIO/RED0.0V0.0V4L30E T/Mission
F44Bank 1 HO2S 2 Heater
GroundORN/WHT0.0V0.0VGeneral Description and
Operation, Catalyst Monitor
HO2S 2
F45A/C RequestGRN/BLK0.0V0.0VChassis Electrical
F46Stop Lamp SwitchBRN/RED0.0V0.0VChassis Electrical
F47Adaptor CaseVIO/WHTB+B+4L30E T/Mission
F48Throttle Valve DC Motor(±:
REV)BLUDuty CycleDuty CycleGeneral Description and
Operation, ETC
F49Not UsedÐÐÐÐ
F50Bank 2 HO2S 2 GroundORN0.0V0.0VÐ
F51Not UsedÐÐÐÐ
F52Bank 1 HO2S 2 GroundRED0.0V0.0VÐ
F53ECT GroundYEL/BLK0.0V0.0VGeneral Description and
Operation, ECT Sensor
F54Vapor Pressure (Fuel Tank
Pressure) Sensor GroundGRN0.0V0.0VGeneral Description and
Operation, VP Sensor
F55Not UsedÐÐÐÐ
F56Injector Cylinder #5GRN/BLKB+B+General Description and
Operation, Fuel Injector
F57Ignition FeedRED/WHTB+B+Chassis Electrical
F58Class 2 DataORN/BLK0.0V0.0VGeneral Description
F59Not UsedÐÐÐÐ
F60Not UsedÐÐÐÐ

6E±25
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
PCM Pinout Table, 80-Way Red Connector ± Row ªS61 ~ 80º
060RY00051
PINPIN FunctionWire ColorIGN ONENG RUNRefer To
S61Intake Air Temperature
(IAT) Sensor GroundYEL/GRN0.0V0.0VGeneral Description and
Operation, IAT
S62ION Sensing ModuleRED1.555V1.555VGeneral Description and
Operation, ION Sensing
Module
S63Bank 1 HO2S 2 HighWHT0.3V0.1±0.9VGeneral Description and
Operation, Catalyst Monitor
HO2S
S64Bank 2 HO2S 1 HighPNK0.3V0.1±0.9VGeneral Description and
Operation, Catalyst Monitor
HO2S
S65Bank 2 HO2S 2 HighGRN0.3V0.1±0.9VGeneral Description and
Operation, Catalyst Monitor
HO2S
S66Transmission Fluid
Temperature SensorRED/BLK0.5±4.9V
(depends on
temperature)0.5±4.9V
(depends on
temperature)4L30E T/Mission
S67Exhaust Gas Recirculation
(EGR) Position SignalGRY/RED0.6V0.6VGeneral Description and
Operation, EGR Control
S68Accelerator Position (AP)
Sensor 1WHT0.41±0.45V0.41±0.45VOn-Vehicle Service
S69Throttle Valve DC
Motor(+: FWD)GRNDuty CycleDuty CycleGeneral Description and
Operation, ETC
S70Not UsedÐÐÐÐ
S71Not UsedÐÐÐÐ
S72Ignition FeedRED/GRNB+B+Chassis Electrical
S73Auto Cruise Main LampGRN/WHTB+B+Chassis Electrical
S74Variable Intake ManifoldYEL/BLK0.0VB+ (rpm
3600 over)General Description
S75Canister Purge Cut
Solenoid ValveRED/WHT6.0V Tank
empty5.7V Tank
emptyGeneral Description and
Operation, EVAP
S76Throttle Position (TP) 1
Sensor SignalBLU0.5±0.8V0.5±0.8V (at
idle)General Description and
Operation, TPS

6E±34
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
dissatisfaction. The following list of non-vehicle faults
does not include every possible fault and may not apply
equally to all product lines.
Fuel Quality
Fuel quality is not a new issue for the automotive industry,
but its potential for turning on the MIL (ªCheck Engineº
lamp) with OBD II systems is new.
Fuel additives such as ªdry gasº and ªoctane enhancersº
may affect the performance of the fuel. If this results in an
incomplete combustion or a partial burn, it will show up as
a Misfire DTC P0300. The Reed Vapor Pressure of the
fuel can also create problems in the fuel system,
especially during the spring and fall months when severe
ambient temperature swings occur. A high Reed Vapor
Pressure could show up as a Fuel Trim DTC due to
excessive canister loading. High vapor pressures
generated in the fuel tank can also affect the Evaporative
Emission diagnostic as well.
Using fuel with the wrong octane rating for the vehicle
may cause driveability problems. Many of the major fuel
companies advertise that using ªpremiumº gasoline will
improve the performance of the vehicle. Most premium
fuels use alcohol to increase the octane rating of the fuel.
Although alcohol-enhanced fuels may raise the octane
rating, the fuel's ability to turn into vapor in cold
temperatures deteriorates. This may affect the starting
ability and cold driveability of the engine.
Low fuel levels can lead to fuel starvation, lean engine
operation, and eventually engine misfire.
Non-OEM Parts
All of the OBD II diagnostics have been calibrated to run
with OEM parts. Something as simple as a
high-performance exhaust system that affects exhaust
system back pressure could potentially interfere with the
operation of the EGR valve and thereby turn on the MIL
(ªCheck Engineº lamp). Small leaks in the exhaust
system near the post catalyst oxygen sensor can also
cause the MIL (ªCheck Engineº lamp) to turn on.
Aftermarket electronics, such as transceivers, stereos,
and anti-theft devices, may radiate EMI into the control
system if they are improperly installed. This may cause a
false sensor reading and turn on the MIL (ªCheck Engineº
lamp).
Environment
Temporary environmental conditions, such as localized
flooding, will have an effect on the vehicle ignition system.
If the ignition system is rain-soaked, it can temporarily
cause engine misfire and turn on the MIL (ªCheck Engineº
lamp).
Refueling
A new OBD II diagnostic was introduced in 1996 on some
vehicles. This diagnostic checks the integrity of the entire
evaporative emission system. If the vehicle is restarted
after refueling and the fuel cap is not secured correctly,
the on-board diagnostic system will sense this as a
system fault and turn on the MIL (ªCheck Engineº lamp)
with a DTC P0440.Vehicle Marshaling
The transportation of new vehicles from the assembly
plant to the dealership can involve as many as 60 key
cycles within 2 to 3 miles of driving. This type of operation
contributes to the fuel fouling of the spark plugs and will
turn on the MIL (ªCheck Engineº lamp) with a P0300
Misfire DTC.
Poor Vehicle Maintenance
The sensitivity of OBD II diagnostics will cause the MIL
(ªCheck Engineº lamp) to turn on if the vehicle is not
maintained properly. Restricted air filters, fuel filters, and
crankcase deposits due to lack of oil changes or improper
oil viscosity can trigger actual vehicle faults that were not
previously monitored prior to OBD II. Poor vehicle
maintenance can't be classified as a ªnon-vehicle faultº,
but with the sensitivity of OBD II diagnostics, vehicle
maintenance schedules must be more closely followed.
Related System Faults
Many of the OBD II system diagnostics will not run if the
PCM detects a fault on a related system or component.
One example would be that if the PCM detected a Misfire
fault, the diagnostics on the catalytic converter would be
suspended until Misfire fault was repaired. If the Misfire
fault was severe enough, the catalytic converter could be
damaged due to overheating and would never set a
Catalyst DTC until the Misfire fault was repaired and the
Catalyst diagnostic was allowed to run to completion. If
this happens, the customer may have to make two trips to
the dealership in order to repair the vehicle.
Emissions Control Information Label
The engine compartment ªVehicle Emissions Control
Information Labelº contains important emission
specifications and setting procedures. In the upper left
corner is exhaust emission information. This identifies
the emission standard (Federal, California, or Canada) of
the engine, the displacement of the engine in liters, the
class of the vehicle, and the type of fuel metering system.
There is also an illustrated emission components and
vacuum hose schematic.
This label is located in the engine compartment of every
vehicle. If the label has been removed it should be
replaced. It can be ordered from Isuzu Dealership.
Visual / Physical Engine Compartment
Inspection
Perform a careful visual and physical engine
compartment inspection when performing any diagnostic
procedure or diagnosing the cause of an emission test
failure. This can often lead to repairing a problem without
further steps. Use the following guidelines when
performing a visual/physical inspection:

Inspect all vacuum hoses for pinches, cuts,
disconnections, and proper routing.

Inspect hoses that are difficult to see behind other
components.

6E±35
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Inspect all wires in the engine compartment for proper
connections, burned or chafed spots, pinched wires,
contact with sharp edges or contact with hot exhaust
manifolds or pipes.
Basic Knowledge of Tools Required
NOTE: Lack of basic knowledge of this powertrain when
performing diagnostic procedures could result in an
incorrect diagnosis or damage to powertrain
components. Do not attempt to diagnose a powertrain
problem without this basic knowledge.
A basic understanding of hand tools is necessary to effec-
tively use this section of the Service Manual.
Serial Data Communications
Class 2 Serial Data Communications
Government regulations require that all vehicle
manufacturers establish a common communication
system. This vehicle utilizes the ªClass 2º communication
system. Each bit of information can have one of two
lengths: long or short. This allows vehicle wiring to be
reduced by transmitting and receiving multiple signals
over a single wire. The messages carried on Class 2 data
streams are also prioritized. If two messages attempt to
establish communications on the data line at the same
time, only the message with higher priority will continue.
The device with the lower priority message must wait.
The most significant result of this regulation is that it
provides Scan tool manufacturers with the capability to
access data from any make or model vehicle that is sold.
The data displayed on other Scan tools will appear the
same, with some exceptions. Some Scan tools will only
be able to display certain vehicle parameters as values
that are a coded representation of the true or actual value.
On this vehicle the Scan tool displays the actual values for
vehicle parameters. It will not be necessary to perform
any conversions from coded values to actual values.
On-Board Diagnostic (OBD II)
On-Board Diagnostic Tests
A diagnostic test is a series of steps, the result of which is
a pass or fail reported to the diagnostic executive. When
a diagnostic test reports a pass result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The diagnostic test has passed during the current
ignition cycle.

The fault identified by the diagnostic test is not
currently active.
When a diagnostic test reports a fail result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The fault identified by the diagnostic test is currently
active.

The fault has been active during this ignition cycle.

The operating conditions at the time of the failure.Remember, a fuel trim DTC may be triggered by a list of
vehicle faults. Make use of all information available (other
DTCs stored, rich or lean condition, etc.) when
diagnosing a fuel trim fault.
Comprehensive Component Monitor
Diagnostic Operation
Comprehensive component monitoring diagnostics are
required to monitor emissions-related input and output
powertrain components. The
CARB OBD II
Comprehensive Component Monitoring List Of
Components Intended To illuminate MIL
is a list of
components, features or functions that could fall under
this requirement.
Input Components:
Input components are monitored for circuit continuity and
out-of-range values. This includes rationality checking.
Rationality checking refers to indicating a fault when the
signal from a sensor does not seem reasonable, i.e.
Throttle Position (TP) sensor that indicates high throttle
position at low engine loads or MAP voltage. Input
components may include, but are not limited to the
following sensors:

Vehicle Speed Sensor (VSS)

Crankshaft Position (CKP) sensor

Throttle Position (TP) sensor

Engine Coolant Temperature (ECT) sensor

Manifold Absolute Pressure (MAP) sensor

Mass Air Flow (MAF) sensor
In addition to the circuit continuity and rationality check,
the ECT sensor is monitored for its ability to achieve a
steady state temperature to enable closed loop fuel
control.
Output Components:
Output components are diagnosed for proper response to
control module commands. Components where
functional monitoring is not feasible will be monitored for
circuit continuity and out-of-range values if applicable.
Output components to be monitored include, but are not
limited to, the following circuits:

Control module controlled EVAP Canister Purge
Valve

Electronic Transmission controls

A/C relays

VSS output

MIL control

Cruise control inhibit
Refer to PCM and Sensors in General Descriptions.
Passive and Active Diagnostic Tests
A passive test is a diagnostic test which simply monitors a
vehicle system or component. Conversely, an active test,
actually takes some sort of action when performing
diagnostic functions, often in response to a failed passive
test. For example, the EGR diagnostic active test will
force the EGR valve open during closed throttle decel
and/or force the EGR valve closed during a steady state.
Either action should result in a change in manifold
pressure.