ISUZU AXIOM 2002 Service Repair Manual

6E±54
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Injector Balance Test
This test is conducted to make sure the appropriate
electric signals are being sent to injectors Nos. 1±6.
Tech 2 must be used for this test.
Test Procedure:
1. Connect Tech 2 to the vehicle DLC.
2. Run the Engine at idle.
3. Select F3: Miscellaneous Test in the Application
Menu.
060R100078
4. Select F7: Injector Balance Test in the Miscellaneous
Test.
060RY00086
5. Select injector number and push ªinjector offº soft key.
060RY00105
6. Make sure of engine speed change.
7. If engine speed changes, the injector electric circuit is
normal.
If engine speed does not change, the injector electric
circuit or the injector itself is not normal.
Plotting Snapshot Graph
This test selects several necessary items from the data
list to plot graphs and makes data comparison on a long
term basis. It is an effective test particularly in emission
related evaluations.
060RX037
For trouble diagnosis, you can collect graphic data (snap
shot) directly from the vehicle.
You can replay the snapshot data as needed. Therefore,
accurate diagnosis is possible, even though the vehicle is
not available.

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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Plotting Graph Flow Chart (Plotting graph after obtaining vehicle information)
060R200070

6E±56
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Flow Chart for Snapshot Replay (Plotting Graph)
060R200072

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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Primary System-Based Diagnostic
Primary System-Based Diagnostic
There are primary system-based diagnostics which
evaluate system operation and its effect on vehicle
emissions. The primary system-based diagnostics are
listed below with a brief description of the diagnostic
function:
Oxygen Sensor Diagnosis
The fuel control heated oxygen sensors (Bank 1 HO2S 1
and Bank 2 HO2S 1) are diagnosed for the following
conditions:

Heater performance (time to activity on cold start)

Slow response

Response time (time to switch R/L or L/R)

Inactive signal (output steady at bias voltage ±
approx. 450 mV)

Signal fixed high

Signal fixed low
The catalyst monitor heated oxygen sensors (Bank 1
HO2S 2 and Bank 2 HO2S 2) are diagnosed for the
following conditions:

Heater performance (time to activity on cold start).

Signal fixed low during steady state conditions or
power enrichment (hard acceleration when a rich
mixture should be indicated).

Signal fixed high during steady state conditions or
deceleration mode (deceleration when a lean mixture
should be indicated).

Inactive sensor (output steady at approx. 438 mV).
If the oxygen sensor pigtail wiring, connector or terminal
are damaged, the entire oxygen sensor assembly must
be replaced. DO NOT attempt to repair the wiring,
connector or terminals. In order for the sensor to function
properly, it must have clean reference air provided to it.
This clean air reference is obtained by way of the oxygen
sensor wire(s). Any attempt to repair the wires, connector
or terminals could result in the obstruction of the
reference air and degrade oxygen sensor performance.
Refer to
On-Vehicle Service, Heated Oxygen Sensors in
this section.
Fuel Control Heated Oxygen Sensor
The main function of the fuel control heated oxygen
sensors is to provide the control module with exhaust
stream oxygen content information to allow proper fueling
and maintain emissions within mandated levels. After it
reaches operating temperature, the sensor will generate
a voltage, inversely proportional to the amount of oxygen
present in the exhaust gases. The control module uses
the signal voltage from the fuel control heated oxygen
sensors while in closed loop to adjust fuel injector pulse
width. While in closed loop, the PCM can adjust fuel
delivery to maintain an air/fuel ratio which allows the best
combination of emission control and driveability. The fuel
control heated oxygen sensors are also used to
determine catalyst efficiency.
HO2S Heater
Heated oxygen sensors are used to minimize the amount
of time required for closed loop fuel control to begin
operation and to allow accurate catalyst monitoring. The
oxygen sensor heater greatly decreases the amount of
time required for fuel control sensors (Bank 1 HO2S 1 and
Bank2 HO2S 1) to become active. Oxygen sensor
heaters are required by catalyst monitor and sensor
(Bank 1 HO2S 2 and Bank 2 HO2S 2) to maintain a
sufficiently high temperature which allows accurate
exhaust oxygen content readings further away from the
engine.
Catalyst Monitor Heated Oxygen Sensors
and Diagnostic Operation
TS24067
To control emissions of hydrocarbons (HC), carbon
monoxide (CO), and oxides of nitrogen (NOx), a
three-way catalytic converter is used. The catalyst within
the converter promotes a chemical reaction which
oxidizes the HC and CO present in the exhaust gas,
converting them into harmless water vapor and carbon
dioxide. The catalyst also reduces NOx, converting it to
nitrogen. The PCM has the ability to monitor this process
using the pre-catalyst and post-catalyst heated oxygen
sensors. The pre-catalyst sensor produces an output
signal which indicates the amount of oxygen present in
the exhaust gas entering the three-way catalytic
converter. The post-catalyst sensor produces an output
signal which indicates the oxygen storage capacity of the
catalyst; this in turn indicates the catalyst's ability to
convert exhaust gases efficiently. If the catalyst is
operating efficiently, the pre-catalyst signal will be far
more active than that produced by the post-catalyst
sensor.
In addition to catalyst monitoring, the heated oxygen
sensors have a limited role in controlling fuel delivery. If
the sensor signal indicates a high or low oxygen content
for an extended period of time while in closed loop, the
PCM will adjust the fuel delivery slightly to compensate.

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6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

For the 3.5L w/automatic transmission, the
pre-catalyst sensors are designated Bank 1 HO2S 1
and Bank 2 HO2S 1. The post-catalyst sensors are
Bank 1 HO2S 2 and Bank 2 HO2S 2.
Catalyst Monitor Outputs
The catalyst monitor diagnostic is sensitive to the
following conditions:

Exhaust leaks

HO2S contamination

Alternate fuels
Exhaust system leaks may cause the following:

Preventing a degraded catalyst from failing the
diagnostic.

Causing a false failure for a normally functioning
catalyst.

Preventing the diagnostic from running.
Some of the contaminants that may be encountered are
phosphorus, lead, silica, and sulfur. The presence of
these contaminants will prevent the TWC diagnostic from
functioning properly.
Three-Way Catalyst Oxygen Storage Capacity
The Three-Way catalyst (TWC) must be monitored for
efficiency. To accomplish this, the control module
monitors the pre-catalyst HO2S and post-catalyst HO2S
oxygen sensors. When the TWC is operating properly,
the post-catalyst oxygen sensor will have significantly
less activity than the pre-catalyst oxygen sensor. The
TWC stores and releases oxygen as needed during its
normal reduction and oxidation process. The control
module will calculate the oxygen storage capacity using
the difference between the pre-catalyst and post catalyst
oxygen sensor's voltage levels. If the activity of the
post-catalyst oxygen sensor approaches that of the
pre-catalyst oxygen sensor, the catalyst's efficiency is
degraded.
Stepped or staged testing level allow the control module
to statistically filter test information. This prevents falsely
passing or falsely failing the oxygen storage capacity test.
The calculations performed by the on-board diagnostic
system are very complex. For this reason, post catalyst
oxygen sensor activity should not be used to determine
oxygen storage capacity unless directed by the service
manual.
Two stages are used to monitor catalyst efficiency.
Failure of the first stage will indicate that the catalyst
requires further testing to determine catalyst efficiency.
The seconds stage then looks at the inputs for the pre and
post catalyst HO2S sensors more closely before
determining if the catalyst is indeed degraded. This
further statistical processing is done to increase the
accuracy of oxygen storage capacity type monitoring.
Failing the first (stage 1) test DOES NOT indicate a failed
catalyst. The catalyst may be marginal or the fuel sulfur
content could be very high.Aftermarket HO2S characteristics may be different from
the original equipment manufacturer sensor. This may
lead to a false pass or a false fail of the catalyst monitor
diagnostic. Similarly, if an aftermarket catalyst does not
contain the same amount of cerium as the original part,
the correlation between oxygen storage and conversion
efficiency may be altered enough to set a false DTC.
Misfire Monitor Diagnostic Operation
Misfire Monitor Diagnostic Operation
Misfire is monitored as a function of the combustion
quality (CQ) signals generated from the ignition current
sense system. Combustion signals represent the degree
of combustion in each cylinder. Misfire is detected when
the combustion signal is below a predetermined value.
The misfire ratio is calculated once every 100 engine
cycles. For example, on a 6-cylinder engine, 600 ignition
plug sparks occur every 100 cycles and if a misfire occurs
12 times during that time, the misfire is 12/600 y 100 = 2
%.
Misfire Counters
Whenever a cylinder misfires, the misfire diagnostic
counts the misfire and notes the crankshaft position at the
time the misfire occurred. These ªmisfire countersº are
basically a file on each engine cylinder. A current and a
history misfire counter are maintained for each cylinder.
The misfire current counters (Misfire Cur #1-6) indicate
the number of firing events out of the last 100 cylinder
firing events which were misfires. The misfire current
counter will display real time data without a misfire DTC
stored. The misfire history counters (Misfire Hist #1-6)
indicate the total number of cylinder firing events which
were misfires. The misfire history counters will display 0
until the misfire diagnostic has failed and a DTC P0300 is
set. Once the misfire DTC P0300 is set, the misfire
history counters will be updated every 100 cylinder firing
events. A misfire counter is maintained for each cylinder.
If the misfire diagnostic reports a failure, the diagnostic
executive reviews all of the misfire counters before
reporting DTC. This way, the diagnostic executive
reports the most current information.
When crankshaft rotation is erratic, a misfire condition will
be detected. Because of this erratic condition, the data
that is collected by the diagnostic can sometimes
incorrectly identify which cylinder is misfiring. Misfires are
counted from more than one cylinder. Cylinder #1 has the
majority of counted misfires. In this case, the Misfire
Counters would identify cylinder #1 as the misfiring
cylinder. The misfires in the other counters were just
background noise caused by the erratic misfire rotation of
the crankshaft. If the number of accumulated misfires is
sufficient for the diagnostic to identify a true misfire, the
diagnostic will set DTC P0300 ± Misfire Detected.
Use diagnostic equipment to monitor misfire counter data
on OBD II-compliant vehicles. Knowing which specific
cylinder(s) misfired can lead to the root cause, even when
dealing with a multiple cylinder misfire. Using the
information in the misfire counters, identify which
cylinders are misfiring. If the counter indicate cylinders

6E±59
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
numbers 1 and 4 misfired, look for a circuit or component
common to both cylinders number 1 and 4.
Misfire counter information is located in the ªEngº. menu,
ªMisfire Dataº sub-menu of the data list.
The misfire diagnostic may indicate a fault due to a
temporary fault not necessarily caused by a vehicle
emission system malfunction. Examples include the
following items:

Contaminated fuel

Low fuel

Fuel-fouled spark plugs

Basic engine fault
Fuel Trim System Monitor Diagnostic
Operation
Fuel Trim System Monitor Diagnostic
Operation
This system monitors the averages of short-term and
long-term fuel trim values. If these fuel trim values stay at
their limits for a calibrated period of time, a malfunction is
indicated. The fuel trim diagnostic compares the
averages of short-term fuel trim values and long-term fuel
trim values to rich and lean thresholds. If either value is
within the thresholds, a pass is recorded. If both values
are outside their thresholds, a rich or lean DTC will be
recorded.
The fuel trim system diagnostic also conducts an intrusive
test. This test determines if a rich condition is being
caused by excessive fuel vapor from the EVAP canister.
In order to meet OBD II requirements, the control module
uses weighted fuel trim cells to determine the need to set
a fuel trim DTC. A fuel trim DTC can only be set if fuel trim
counts in the weighted fuel trim cells exceed
specifications. This means that the vehicle could have a
fuel trim problem which is causing a problem under
certain conditions (i.e., engine idle high due to a small
vacuum leak or rough idle due to a large vacuum leak)
while it operates fine at other times. No fuel trim DTC
would set (although an engine idle speed DTC or HO2S
DTC may set). Use the Tech 2 to observe fuel trim counts
while the problem is occurring.
A fuel trim DTC may be triggered by a number of vehicle
faults. Make use of all information available (other DTCs
stored, rich or lean condition, etc.) when diagnosing a fuel
trim fault.
Fuel Trim Cell Diagnostic Weights
No fuel trim DTC will set regardless of the fuel trim counts
in cell 0 unless the fuel trim counts in the weighted cells
are also outside specifications. This means that the
vehicle could have a fuel trim problem which is causing a
problem under certain conditions (i.e. engine idle high due
to a small vacuum leak or rough due to a large vacuum
leak) while it operates fine at other times. No fuel trim
DTC would set (although an engine idle speed DTC or
HO2S DTC may set). Use the Tech 2 to observe fuel trim
counts while the problem is occurring.

6E±60
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD II) System Check
060R200048
Circuit Description
The on-board diagnostic system check is the starting
point for any driveability complaint diagnosis. Before
using this procedure, perform a careful visual/physical
check of the PCM and engine grounds for cleanliness and
tightness.
The on-board diagnostic system check is an organized
approach to identifying a problem created by an
electronic engine control system malfunction.
Diagnostic Aids
An intermittent may be caused by a poor connection,
rubbed±through wire insulation or a wire broken inside the
insulation. Check for poor connections or a damaged
harness. Inspect the PCM harness and connector for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire connection,
and damaged harness.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1.The MIL (ªCheck Engine lampº) should be ªONº
steady with the ignition ªON º and the engine ªOFFº.
If not, the ªNo MILº chart should be used to isolate
the malfunction.
2.The RPL (ªReduced Power lampº) should be ªONº
steady with the ignition ªON ºand the engine ªOFFº.
If not, the ªNo RPLºchart should be used to isolate
the malfunction.3.Checks the Class 2 data circuit and ensures that the
PCM is able to transmit serial data.
4.This test ensures that the PCM is capable of
controlling the MIL (ªCheck Engine lampº) and the
MIL (ªCheck Engine lampº) driver circuit is not
shorted to ground.
5.This test ensures that the PCM is capable of
controlling the RPL (ªReduced Power lampº) and
the RPL (ªReduced Power lampº) driver circuit is not
shorted to ground.
7.Check the DTCs (System ,Volts Supply circuit).
8.Check the DTCs (PCM{Software} detect Errors).
11.If the engine will not start, the Cranks But Will Not
Run chart should be used to diagnose the condition.
14.A Tech 2 parameter which is not within the typical
range may help to isolate the area which is causing
the problem.
15.This vehicle is equipped with a PCM which utilizes
an electrically erasable programmable read only
memory (EEPROM). When the PCM is replaced,
the new PCM must be programmed. Refer to PCM
Replacement and Programming Procedures in
Powertrain Control Module (PCM) and Sensors
of
this section.
10. If the starter motor will not start, the starter control
system chart should be used to diagnose the
condition.

6E±61
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD II) System Check

StepActionValue(s)Ye sNo
11. Ignition ªONº, engine ªOFFº.
2. Observe the malfunction indicator lamp (MIL or
ªCheck Engine lampº).
Is the MIL (ªCheck Engine lampº)ªONº?
ÐGo to Step 2
Go to No
MIL(ªCheck
Engine lampº)
21. Ignition ªONº, engine ªOFFº.
2. Observe the ªReduced Power lampº.
Is the RPL (ªReduced Power lampº) ªONº?
ÐGo to Step 3
Go to No
RPL(ªReduce
d Power
lampº)
31. Ignition ªOFFº.
2. Install Tech 2.
3. Ignition ªONº.
4. Attempt to display PCM engine data with the
Tech 2.
Does the Tech 2 display PCM data?
ÐGo to Step 4Go to Step 12
41. Using the Tech 2 output tests function, select MIL
(ªCheck Engine lampº) control and command the
MIL (ªCheck Engine Lampº) ªOFFº.
2. Observe the MIL (ªCheck Engine lampº).
Did the MIL (ªCheck Engine lampº) turn ªOFFº?
ÐGo to Step 5
Go to
MIL(ªCheck
Engine lampº)
On Steady
51. Using the Tech 2 output tests function, select MIL
(ªCheck Engine lampº) control and command the
RPL (ªReduced Power lampº) ªOFFº.
2. Observe the RPL (ªReduced Power lampº).
Did the MIL (ªReduced Power lampº) turn ªOFFº?
ÐGo to Step 6
Go to
RPL(ªReduce
d Power
lampº) On
Steady
6Select ªDisplay DTCsº with the Tech 2.
Are any DTCs stored?
ÐGo to Step 7Go to Step 11
7Stored DTCs.
P0562, P0563, P0601, P0602, P0604, P0606, P1625,
P1635, P1639, P1640, P1650
Are the applicable DTCs stored?
Ð
Go to
applicable
DTC table
Go to Step 8
8Stored DTCs.
P1514, P1515, P1516, P1523, P1125, P1290, P1295,
P1299
Are the applicable DTCs stored?
Ð
Go to
applicable
DTC table
Go to Step 9
9Stored DTCs.
1. P0425, P0106, P0107, P1107, P0401, P1404,
P0405, P1120, P1221, P1515, P1516, P1275,
P1635, P1271, P1273, P1285, P1272
2. P0336, P0337, P1220, P1515, P1221, P1516,
P1280, P1639, P1271, P1272
Are the applicable DTCs stored?
Ð
Go to
ªMultiple
PCM
Information
sensor DTCs
Setº
Go to Step 10
10Attempt to crank the starter motor
Did the starter motor crank?
ÐGo to Step 10
Go to Starter
control
system
11Attempt to start the engine.
Did the engine start and continue to run?
ÐGo to Step 6
Go to Cranks
But Will Not
Run

6E±62
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
On-Board Diagnostic (OBD II) System Check

 
StepNo Ye s Value(s) Action
12Compare PCM data values displayed on the Tech 2 to
the typical engine scan data values.
Are the displayed values normal or close to the typical
values?
Ð
Go to
Symptom
Refer to
indicated
Component
System
Checks
131. Ignition ªOFFº, disconnect the PCM.
2. Ignition ªONº, engine ªOFFº.
3. Check the Class 2 data circuit for an open, short to
ground, or short to voltage. Also, check the DLC
ignition feed circuit for an open or short to ground
and the DLC ground circuit for an open.
4. If a problem is found, repair as necessary.
Was a problem found?
ÐGo to Step 2Go to Step 14
141. Attempt to reprogram the PCM. Refer to Powertrain
Control Module (PCM) in On-Vehicle Service.
2. Attempt to display PCM data with the Tech 2.
Does the Tech 2 display PCM engine data?
ÐGo to Step 2Go to Step 15
15Replace the PCM.
IMPORTANT:The replacement PCM must be
programmed. Refer to
ON-Vehicle Service in Power
Control Module and Sensors for procedures.
And also refer to latest Service Bulletin. Check to see
if the latest software is released or not. And then Down
Load the LATEST PROGRAMMED SOFTWARE to the
replacement PCM.
Is the action complete?
ÐGo to Step 2Ð

6E±63
6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS
A/C Clutch Control Circuit Diagnosis
060R100063
Circuit Description
When air conditioning and blower fan are selected, and if
the system has a sufficient refrigerant charge, a 12-volt
signal is supplied to the A/C request input of the
powertrain control module (PCM). The A/C request
signal may be temporarily canceled during system
operation by the electronic thermostat in the evaporator
case. When the A/C request signal is received by the
PCM, the PCM supplies a ground from the compressor
clutch relay if the engine operating conditions are within
acceptable ranges. With the A/C compressor relay
energized, voltage is supplied to the compressor clutch
coil.
The PCM will enable the compressor clutch to engage
whenever A/C has been selected with the engine running,
unless any of the following conditions are present:

The throttle is greater than 90%.

The ignition voltage is below 10.5 volts.

The engine speed is greater than 4500 RPM for 5
seconds or 5400 RPM.
The engine coolant temperature (ECT) is greater
than 125
C (257
F).

The intake air temperature (IAT) is less than 5
C
(41
F).

The power steering pressure switch signals a high
pressure condition.
Diagnostic Aids
To diagnose an the intermittent fault, check for following
conditions:

Poor connection at the PCM±Inspect connections for
backed-out terminals, improper mating, broken locks,
improperly formed or damaged terminals, and poor
terminal-to-wire connection.

Damaged harness±Inspect the wiring harness for
damage. If the harness appears to OK, observe the
A/C clutch while moving connectors and wiring
harnesses related to the A/C. A sudden clutch
malfunction will indicate the source of the intermittent
fault.