2002 ISUZU AXIOM check engine

6E±2
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Fuel Trim System Monitor Diagnostic
Operation 6E±59. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Trim System Monitor Diagnostic
Operation 6E±59. . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Trim Cell Diagnostic Weights 6E±59. . . . . . .
On-Board Diagnostic (OBD II) System Check 6E±60
Circuit Description 6E±60. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±60. . . . . . . . . . . . . . . . . . . . . . . .
Test Description 6E±60. . . . . . . . . . . . . . . . . . . . . . .
A/C Clutch Control Circuit Diagnosis 6E±63. . . . . . .
Circuit Description 6E±63. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±63. . . . . . . . . . . . . . . . . . . . . . . .
A/C Clutch Diagnosis 6E±64. . . . . . . . . . . . . . . . . .
Electronic Ignition System Diagnosis 6E±68. . . . . . .
EVAP Canister Purge Solenoid and EVAP
Vent Solenoid Valve 6E±68. . . . . . . . . . . . . . . . . . . . .
Visual Check of The Evaporative Emission
Canister 6E±68. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Fuel Metering System Check 6E±68. . . . . . . . . . . . .
Fuel System Pressure Test 6E±68. . . . . . . . . . . . . . .
Fuel Injector Coil Test Procedure and Fuel
Injector Balance Test Procedure 6E±68. . . . . . . . . .
Test Description 6E±68. . . . . . . . . . . . . . . . . . . . . . .
Injector Coil Test Procedure (Steps 1-6)
and Injector Balance Test Procedure
(Steps 7-11) 6E±69. . . . . . . . . . . . . . . . . . . . . . . . . .
Powertrain Control Module (PCM) Diagnosis 6E±73
Multiple PCM Information Sensor DTCs Set 6E±73
Circuit Description 6E±73. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±73. . . . . . . . . . . . . . . . . . . . . . . .
Exhaust Gas Recirculation (EGR) Diagnosis 6E±76
Engine Tech 2 Data Definitions and Ranges 6E±76
Typical Scan Data Values 6E±78. . . . . . . . . . . . . . . .
Test Conditions 6E±78. . . . . . . . . . . . . . . . . . . . . . . .
No Malfunction Indicator Lamp (MIL) 6E±84. . . . . . .
Circuit Description 6E±84. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±84. . . . . . . . . . . . . . . . . . . . . . . .
Malfunction Indicator Lamp (MIL) ªONº
Steady 6E±87. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit description 6E±87. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±87. . . . . . . . . . . . . . . . . . . . . . . .
No Reduced Power Lamp (RPL) 6E±89. . . . . . . . . .
Circuit Description 6E±89. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±89. . . . . . . . . . . . . . . . . . . . . . . .
Test Description 6E±89. . . . . . . . . . . . . . . . . . . . . . .
Reduced Power Lamp (RPL) ªONº Steady 6E±93. .
Circuit Description 6E±93. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±93. . . . . . . . . . . . . . . . . . . . . . . .
Test Description 6E±93. . . . . . . . . . . . . . . . . . . . . . .
Starter Control System Check 6E±96. . . . . . . . . . . . .
Circuit Description 6E±96. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±96. . . . . . . . . . . . . . . . . . . . . . . .
Engine Cranks But Will Not Run 6E±100. . . . . . . . . . .
Circuit Description 6E±102. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±102. . . . . . . . . . . . . . . . . . . . . . . . Test Description 6E±102. . . . . . . . . . . . . . . . . . . . . . .
Fuel System Electrical Test 6E±107. . . . . . . . . . . . . . .
Circuit Description 6E±108. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±108. . . . . . . . . . . . . . . . . . . . . . . .
Test Description 6E±108. . . . . . . . . . . . . . . . . . . . . . .
Fuel Pressure Relief Procedure 6E±108. . . . . . . . .
Electric Throttle Control (ETC) System
Check 6E±111. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Description 6E±112. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±112. . . . . . . . . . . . . . . . . . . . . . . .
Test Description 6E±112. . . . . . . . . . . . . . . . . . . . . . .
Fuel System Diagnosis 6E±115. . . . . . . . . . . . . . . . . . .
Circuit Description 6E±116. . . . . . . . . . . . . . . . . . . . .
Test Description 6E±116. . . . . . . . . . . . . . . . . . . . . . .
Fuel Pressure Relief Procedure 6E±117. . . . . . . . .
Exhaust Gas Recirculation (EGR) System
Check 6E±120. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Description 6E±120. . . . . . . . . . . . . . . . . . . . .
Manifold Absolute Pressure (MAP) Output
Check 6E±122. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Circuit Description 6E±122. . . . . . . . . . . . . . . . . . . . .
Evaporative (EVAP) Emissions Canister
Purge Valve Check 6E±124. . . . . . . . . . . . . . . . . . . . .
Circuit Description 6E±124. . . . . . . . . . . . . . . . . . . . .
Diagnostic Aids 6E±124. . . . . . . . . . . . . . . . . . . . . . . .
PCM Diagnostic Trouble Codes 6E±127. . . . . . . . . . .
DTC P0101 MAF System Performance 6E±131. . . .
DTC P0102 MAF Sensor Circuit Low
Frequency 6E±134. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0103 MAF Sensor Circuit High
Frequency 6E±137. . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0106 MAP System Performance 6E±140. . . .
DTC P0107 MAP Sensor Circuit Low
Voltage 6E±143. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0108 MAP Sensor Circuit High
Voltage 6E±146. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0112 IAT Sensor Circuit Low
Voltage 6E±149. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0113 IAT Sensor Circuit High
Voltage 6E±152. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0117 ECT Sensor Circuit Low
Voltage 6E±155. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0118 ECT Sensor Circuit High
Voltage 6E±158. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DTC P0125 ECT Excessive Time to Closed
Loop Fuel Control 6E±161. . . . . . . . . . . . . . . . . . . . . . .
DTC P0128 Thermostat Insufficient
Temperature for Stable Operation 6E±164. . . . . . . . .
DTC P0131 HO2S Circuit Low Voltage
Bank 1 Sensor 1 6E±166. . . . . . . . . . . . . . . . . . . . . . . .
DTC P0132 HO2S Circuit High Voltage
Bank 1 Sensor 1 6E±169. . . . . . . . . . . . . . . . . . . . . . . .
DTC P0133 HO2S Slow Response
Bank 1 Sensor 1 6E±172. . . . . . . . . . . . . . . . . . . . . . . .
DTC P0134 HO2S Circuit Insufficient
Activity Bank 1 Sensor 1 6E±176. . . . . . . . . . . . . . . . .

6E±19
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
PCM Pinout Table, 80-Way Red Connector ± Row ªS1 ~ 20º
060RY00069
PINPIN FunctionWire ColorIGN ONENG RUNRefer To
S1PCM GroundBLK/PNK0.0V0.0VChassis Electrical
S2Bank 1 HO2S 1 Heater
GroundBLK/ORN0.0V0.0VGeneral Description and
Operation, Catalyst Monitor
HO2S
S3Not UsedÐÐÐÐ
S4Not UsedÐÐÐÐ
S55Volt Referenceª2º (CKP
Sensor)WHT5.0V5.0VAppropriate Sensor (CKP
Sensor, AP2 Sensor)
S6Auto Cruise Switch CancelGRY/GRN0.0V0.0VChassis Electrical
S7Purge Duty Solenoid ValveRED/BLUB+B+EVAP Emission Control
System
S8M.I.D0.5 GRNÐÐÐ
S9Not UsedÐÐÐÐ
S10Shift High (Band Apply)BRN/YELB+B+4L30E T/Mission
S11Malfunction Indicator
(Check Engine) LampWHT/GRN0.0VB+Chassis Electrical
S12Not UsedÐÐÐÐ
S13ION Sensing ModuleRED/WHT1.555V1.555VGeneral Description and
Operation, ION Sensing
Module
S14Bank 2 HO2S 1 GroundBLU0.0V0.0VÐ
S15Bank 2 HO2S 2 GroundORN0.0V0.0VÐ
S16Bank 2 HO2S 2 LowBLU0.0V0.1VGeneral Description and
Operation, Catalyst Monitor
HO2S
S17Bank 1 HO2S 1 GroundWHT0.0V0.0VÐ
S18Bank 1 HO2S 1 LowWHT/BLU0.0V0.1VGeneral Description and
Operation, Catalyst Monitor
HO2S

6E±28
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Engine Component Locator Table
Number
NameLocation
1Linear Exhaust Gas Recirculation (EGR) ValveRear right side of the engine
2Throttle Position (TP) SensorOn the throttle body
3Intake Air Temperature (IAT) SensorOn the intake air duct near the throttle body
4Check Engine (MIL) LightOn the instrument panel beneath the
tachometer
5Positive Crankcase Ventilation (PCV) ValveOn the left of the cylinder head cover
6Air CleanerLeft front of the engine bay
7Mass Air Flow (MAF) SensorAttached to the air filter box
8Fuel RailOn the Common Chamber
9Fuel Pressure RegulatorRear side of the engine
10ION Sensing moduleBolted to the top of the Common Chamber
11Common ChamberTop of the engine
12EVAP Duty Solenoid ValveBolted to the front of the coolant pipe
13Fuse/Relay BoxAlong the inside of the right fender
14Manifold Absolute Pressure (MAP) SensorBolted to the top of the Common Chamber
15Throttle BodyBetween the intake air duct and the Common
Chamber
16Engine Coolant Temperature SensorOn the coolant crossover pipe at the front of
the engine, near the throttle body
17Power Train Control Module (PCM)Along the inside of the left fender

6E±33
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnosis
Strategy-Based Diagnostics
Strategy-Based Diagnostics
The strategy-based diagnostic is a uniform approach to
repair all Electrical/Electronic (E/E) systems. The
diagnostic flow can always be used to resolve an E/E
system problem and is a starting point when repairs are
necessary. The following steps will instruct the technician
how to proceed with a diagnosis:
1. Verify the customer complaint.

To verify the customer complaint, the technician
should know the normal operation of the system.
2. Perform preliminary checks.

Conduct a thorough visual inspection.

Review the service history.

Detect unusual sounds or odors.

Gather diagnostic trouble code information to
achieve an effective repair.
3. Check bulletins and other service information.

This includes videos, newsletters, etc.
4. Refer to service information (manual) system
check(s).

ªSystem checksº contain information on a system
that may not be supported by one or more DTCs.
System checks verify proper operation of the
system. This will lead the technician in an
organized approach to diagnostics.
5. Refer to service diagnostics.
DTC Stored
Follow the designated DTC chart exactly to make an
effective repair.
No DTC
Select the symptom from the symptom tables. Follow the
diagnostic paths or suggestions to complete the repair.
You may refer to the applicable component/system check
in the system checks.
No Matching Symptom
1. Analyze the complaint.
2. Develop a plan for diagnostics.
3. Utilize the wiring diagrams and the theory of
operation.
Combine technician knowledge with efficient use of the
available service information.
Intermittents
Conditions that are not always present are called
intermittents. To resolve intermittents, perform the
following steps:
1. Observe history DTCs, DTC modes, and freeze
frame data.
2. Evaluate the symptoms and the conditions described
by the customer.3. Use a check sheet or other method to identify the
circuit or electrical system component.
4. Follow the suggestions for intermittent diagnosis
found in the service documentation.
Most Scan Tools, such as the Tech 2, have data-capturing
capabilities that can assist in detecting intermittents.
No Trouble Found
This condition exists when the vehicle is found to operate
normally. The condition described by the customer may
be normal. Verify the customer complaint against another
vehicle that is operating normally. The condition may be
intermittent. Verify the complaint under the conditions
described by the customer before releasing the vehicle.
1. Re-examine the complaint.
When the complaint cannot be successfully found or
isolated, a re-evaluation is necessary. The complaint
should be re-verified and could be intermittent as
defined in
Intermittents section, or could be normal.
2. Repair and verify.
After isolating the cause, the repairs should be made.
Validate for proper operation and verify that the
symptom has been corrected. This may involve road
testing or other methods to verify that the complaint
has been resolved under the following conditions:

Conditions noted by the customer.

If a DTC was diagnosed, verify a repair by
duplicating conditions present when the DTC was
set as noted in the Failure Records or Freeze
Frame data.
Verifying Vehicle Repair
Verification of the vehicle repair will be more
comprehensive for vehicles with OBD II system
diagnostics. Following a repair, the technician should
perform the following steps:
IMPORTANT:Follow the steps below when you verify
repairs on OBD II systems. Failure to follow these steps
could result in unnecessary repairs.
1. Review and record the Failure Records and the
Freeze Frame data for the DTC which has been
diagnosed (Freeze Frame data will only be stored for
an A or B type diagnostic and only if the MIL(ºCheck
Engineº lamp) has been requested).
2. Clear the DTC(S).
3. Operate the vehicle within conditions noted in the
Failure Records and Freeze Frame data.
4. Monitor the DTC status information for the DTC which
has been diagnosed until the diagnostic test
associated with that DTC runs.
General Service Information
OBD II Serviceablity Issues
With the introduction of OBD II diagnostics across the
entire passenger car and light-duty truck market in 1996,
illumination of the MIL (ªCheck Engineº lamp) due to a
non-vehicle fault could lead to misdiagnosis of the
vehicle, increased warranty expense and customer

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.

6E±36
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Intrusive Diagnostic Tests
This is any on-board test run by the Diagnostic
Management System which may have an effect on
vehicle performance or emission levels.
Warm-Up Cycle
A warm-up cycle means that engine at temperature must
reach a minimum of 70
C (160
F)
and rise at least 22
C
(40
F) over the course of a trip.
Freeze Frame
Freeze Frame is an element of the Diagnostic
Management System which stores various vehicle
information at the moment an emissions-related fault is
stored in memory and when the MIL is commanded on.
These data can help to identify the cause of a fault. Refer
to
Storing And Erasing Freeze Frame Data in this section
for more detailed information.
Failure Records
Failure Records data is an enhancement of the OBD II
Freeze Frame feature. Failure Records store the same
vehicle information as does Freeze Frame, but it will store
that information for any fault which is stored in on-board
memory, while Freeze Frame stores information only for
emission-related faults that command the MIL on.
System Status and Drive Cycle for
Satisfying Federal Inspection/Maintenance
(I/M 240) Regulations
I/M Ready Status means a signal or flag for each
emission system test that had been set in the PCM. I/M
Ready Status indicates that the vehicle on-board
emissions diagnostics have been run. I/M Ready Status
is not concerned whether the emission system passed or
failed the test, only that on-board diagnosis is complete.
Not all vehicles use all possible I/M flags.
Common OBD II Terms
Diagnostic
When used as a noun, the word diagnostic refers to any
on-board test run by the vehicle's Diagnostic
Management System. A diagnostic is simply a test run on
a system or component to determine if the system or
component is operating according to specification. There
are many diagnostics, shown in the following list:

Misfire

Oxygen sensors

Oxygen sensor heaters

EGR

Catalyst monitoring
Enable Criteria
The term ªenable criteriaº is engineering language for the
conditions necessary for a given diagnostic test to run.
Each diagnostic has a specific list of conditions which
must be met before the diagnostic will run. ªEnable
criteriaº is another way of saying ªconditions requiredº.The enable criteria for each diagnostic is listed on the first
page of the DTC description in Section 6E under the
heading ªConditions for Setting the DTCº. Enable criteria
varies with each diagnostic, and typically includes, but is
not limited to the following items:

engine speed

vehicle speed

ECT

MAF/MAP

barometric pressure

IAT

TP

high canister purge

fuel trim

TCC enabled

A/C on
Trip
Technically, a trip is a key on-run-key off cycle in which all
the enable criteria for a given diagnostic are met, allowing
the diagnostic to run. Unfortunately, this concept is not
quite that simple. A trip is official when all the enable
criteria for a given diagnostic are met. But because the
enable criteria vary from one diagnostic to another, the
definition of trip varies as well. Some diagnostics are run
when the vehicle is at operating temperature, some when
the vehicle first starts up; some require that the vehicle be
cruising at a steady highway speed, some run only when
the vehicle is idle; some diagnostics function with the
TCC disabled. Some run only immediately following a
cold engine start-up.
A trip then, is defined as a key on-run-key off cycle in
which the vehicle was operated in such a way as to satisfy
the enabling criteria for a given diagnostic, and this
diagnostic will consider this cycle to be one trip. However,
another diagnostic with a different set of enable criteria
(which were not met) during this driving event, would not
consider it a trip. No trip will occur for that particular
diagnostic until the vehicle is driven in such a way as to
meet all the enable criteria.
The Diagnostic Executive
The Diagnostic Executive is a unique segment of
software which is designed to coordinate and prioritize
the diagnostic procedures as well as define the protocol
for recording and displaying their results. The main
responsibilities of the Diagnostic Executive are listed as
the following:

Commanding the MIL (ªCheck Engineº lamp) on and
off

DTC logging and clearing

Freeze Frame data for the first emission related DTC
recorded

Non-emission related Service Lamp

Operating conditions Failure Records buffer, (the
number of records will vary)

Current status information on each diagnostic

System Status (I/M ready)

6E±37
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
The Diagnostic Executive records DTCs and turns on the
MIL when emission-related faults occur. It can also turn
off the MIL if the conditions cease which caused the DTC
to set.
Diagnostic Information
The diagnostic charts and functional checks are designed
to locate a faulty circuit or component through a process
of logical decisions. The charts are prepared with the
requirement that the vehicle functioned correctly at the
time of assembly and that there are no multiple faults
present.
There is a continuous self-diagnosis on certain control
functions. This diagnostic capability is complemented by
the diagnostic procedures contained in this manual. The
language of communicating the source of the malfunction
is a system of diagnostic trouble codes. When a
malfunction is detected by the control module, a
diagnostic trouble code is set and the Malfunction
Indicator Lamp (MIL) (ªCheck Engineº lamp) is
illuminated.
Malfunction Indicator Lamp (MIL)
The Malfunction Indicator Lamp (MIL) looks the same as
the MIL you are already familiar with (ªCheck Engineº
lamp). However, OBD II requires that it illuminate under a
strict set of guide lines.
Basically, the MIL is turned on when the PCM detects a
DTC that will impact vehicle emissions.
The MIL is under the control of the Diagnostic Executive.
The MIL will be turned on if an emissions-related
diagnostic test indicates a malfunction has occurred. It
will stay on until the system or component passes the
same test, for three consecutive trips, with no emissions
related faults.
If the vehicle is experiencing a misfire malfunction which
may cause damage to the Three-Way Catalytic
Converter (TWC), the MIL will flash once per second.
This will continue until the vehicle is outside of speed and
load conditions which could cause possible catalyst
damage, and the MIL will stop flashing and remain on
steady.
Extinguishing the MIL
When the MIL is on, the Diagnostic Executive will turn off
the MIL after
three(3) consecutive trips that a ªtest
passedº has been reported for the diagnostic test that
originally caused the MIL to illuminate.
Although the MIL has been turned off, the DTC will remain
in the PCM memory (both Freeze Frame and Failure
Records) until
forty(40) warm-up cycles after no faults
have been completed.
If the MIL was set by either a fuel trim or misfire-related
DTC, additional requirements must be met. In addition to
the requirements stated in the previous paragraph, these
requirements are as follows:

The diagnostic tests that are passed must occur
within 375 RPM of the RPM data stored at the time the
last test failed.

Plus or minus ten (10) percent of the engine load that
was stored at the time the last failed.
Similar engine temperature conditions (warmed up or
warming up ) as those stored at the time the last test
failed.
Meeting these requirements ensures that the fault which
turned on the MIL has been corrected.
The MIL (ªCheck Engineº lamp) is on the instrument
panel and has the following function:

It informs the driver that a fault affects vehicle
emission levels has occurred and that the vehicle
should be taken for service as soon as possible.

As a bulb and system check, the MIL will come ªONº
with the key ªONº and the engine not running. When
the engine is started, the MIL will turn ªOFF.º

When the MIL remains ªONº while the engine is
running, or when a malfunction is suspected due to a
driveability or emissions problem, a Powertrain
On-Board Diagnostic (OBD ll) System Check must be
performed. The procedures for these checks are
given in On-Board Diagnostic (OBD) System Check.
These checks will expose faults which may not be
detected if other diagnostics are performed first.
DTC Types
Each DTC is directly related to a diagnostic test. The
Diagnostic Management System sets DTC based on the
failure of the tests during a trip or trips. Certain tests must
fail two (2) consecutive trips before the DTC is set. The
following are the four (4) types of DTCs and the
characteristics of those codes:

Type A

Emissions related

Requests illumination of the MIL of the first trip with a
fail

Stores a History DTC on the first trip with a fail

Stores a Freeze Frame (if empty)

Stores a Fail Record

Updates the Fail Record each time the diagnostic
test fails

Type B

Emissions related

ªArmedº after one (1) trip with a fail

ªDisarmedº after one (1) trip with a pass

Requests illumination of the MIL on the
second
consecutive trip
with a fail

Stores a History DTC on the second consecutive trip
with a fail (The DTC will be armed after the first fail)

Stores a Freeze Frame on the second consecutive
trip with a fail (if empty)

Stores a Fail Record when the first test fails (not
dependent on
consecutive trip fails)

Updates the Fail Record each time the diagnostic
test fails
(Some special conditions apply to misfire and fuel trim
DTCs)

Type C (if the vehicle is so equipped)

Non-Emissions related

Requests illumination of the Service

Stores a History DTC on the
first trip with a fail