Isuzu Trooper (2000 year). Manual — part 286

6E–273

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0306 Cylinder Misfire Detected

Circuit Description

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.
This DTC P0306 will determine if the No.6 cylinder misfire
is occurring by monitoring the Combustion Quality.

Conditions for Setting the DTC

D

None of the following occur: TP sensor, MAF sensor,
vehicle speed sensor, ECT sensor.

D

The engine speed is between 600 and 6250 RPM.

D

The system voltage is between 11 and 16 volts.

D

The ECT indicates an engine temperature between
–7

°

C (28

°

F) and 120

°

C (248

°

F).

D

The throttle angle is steady.

Action Taken When the DTC Sets

D

The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

D

If the misfire is severe enough to cause possible
catalyst damage, the PCM will flash the MIL for as long
as the misfire remains at catalyst damaging levels.

D

The PCM will store conditions which were present
when the DTC was set as Freeze Frame and in the
Failure Records data.

Conditions for Clearing the MIL/DTC

D

The PCM will turn the MIL “OFF” on the third
consecutive ignition cycle in which the diagnostic has
been run and the fault condition is no longer present.

D

A history DTC P0306 will clear after 40 consecutive
ignition cycles occur without a fault.

D

DTC P0306 can be cleared by using the Tech 2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

Check for the following conditions:

D

System grounds – Ensure all connections are clean
and properly tightened.

D

Injector – Perform the injector coil/balance test to
locate a faulty injector that contributes to a lean
condition on the affected cylinder. In addition to the
above test, check the condition of the injector O-ring.

D

Faulty spark plug – Check for a cracked insulator,
carbon tracking, incorrect gap, and worn electrodes.

D

Damaged or faulty ignition coil – Check for cracks or
other damage.

D

Substitute a known good coil – Swap the ignition coils
and retest. If the misfire follows the coil, replace the
ignition coil.

DTC P0306 – Cylinder Misfire Detected

Step

Action

Value(s)

Yes

No

1

Was the “On-Board Diagnostic (OBD) System Check”
performed?

—

Go to

Step 2

Go to

OBD

System

Check

2

1. Start the engine. Run the engine at idle.
2. Review and record Tech 2 Freeze Frame data.
3. Monitor “Misfire Cur. #6” on the Tech 2.

Is “Misfire Cur. #6” increasing (indicating a misfire
currently occurring)?

—

Go to

Step 4

Go to

Step 3

3

Monitor “Misfire Hist. #6” while operating the vehicle to
duplicate the conditions present when the DTC was set
(as defined by the Freeze Frame data recorded in Step
2).

Is “Misfire Hist. #6” increasing (indicating a misfire
currently occurring)?

—

Go to

Step 4

Refer to

Diagnostic

Aids

4

1. Visually and physically inspect the vacuum hoses

for splits, kinks, and improper connections. Also,
inspect the intake manifold for a vacuum leak.

2. If a problem is found, repair it as necessary.

Did the inspection reveal a problem?

—

Verify repair

Go to

Step 5

5

1. Install a spark tester at the spark plug end of the

cylinder #6 ignition wire.

2. Crank the engine while observing the spark tester.

A crisp, blue spark should be observed.

Is adequate spark present?

—

Go to

Step 8

Go to

Step 6

6E–274

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

DTC P0306 – Cylinder Misfire Detected

(Cont'd)

Step

No

Yes

Value(s)

Action

6

1. Remove and visually/physically inspect the ignition

coil associated with cylinder #6. Ensure that the coil
is free of cracks and carbon tracking.

2. If a problem is found, replace the damaged ignition

coil as necessary.

Did the visual inspection reveal a problem?

—

Verify repair

Go to

Step 7

7

1. Measure the ignition coil primary resistance.
2. If resistance is not within the specified value,

replace the faulty ignition coil.

Did the ignition coil require replacement?

2.6-2.7 K

m

Verify repair

Go to

Step 12

8

Remove the cylinder #6 spark plug and visually inspect
the spark plug electrode.

Does the inspection reveal excessive fouling?

—

Go to

Contaminatio

n Diagnosis

chart in

Engine

Mechanical

Diagnosis

Go to

Step 9

9

1. Visually inspect the spark plug insulator for cracks,

carbon tracking, or other damage.

2. If the spark plug is damaged, replace the spark plug.

Did the inspection reveal a problem?

—

Verify repair

Go to

Step 10

10

1. Perform the “Injector Coil/Balance Test.”
2. If any faulty injectors are found, replace them as

necessary.

Did any of the injectors require replacement?

—

Verify repair

Go to

Step 11

11

1. Inspect the intake manifold and the injector O-rings

for a vacuum leak.

2. If a problem is found, repair it as necessary.

Did the inspection reveal a problem?

—

Verify repair

Go to

Step 12

12

Check for an engine mechanical problem. Refer to
Engine Mechanical Diagnosis to diagnose and repair
the following conditions:

D

A faulty or incorrect camshaft

D

Leaking or sticky valves or rings

D

Excessive valve deposits

D

Weak valve springs

D

A leaking head gasket

Was a basic engine mechanical problem found?

—

Verify repair

Refer to

Diagnostic

Aids

6E–275

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

Diagnostic Trouble Code (DTC) P0325 ION Sensing Module/ION Sensing

Knock Intensity Circuit Fault

D06RY00067

Circuit Description

The Power Control Module (PCM) checks the validity of
the signals used in the ION Sensing module at the
following engine opreating conditions.

D

The test is performed to evauate the Knock Intensity
(KI) signal pulse width if it is within a predetermined
renge. If the KI signal puls width is out of the
predetermined range, the fail counter will be
incremented. If the failure counter excceds the
calibration, then test is complete and a failure will be
reported. If the sample counter threshold is reached
before the failure threshold, then the test is complete
and a pass will be reported. This test will detect an
open/short in the KI line circuit, ION module faults and
analog input faults in the PCM.

Conditions for setting the DTC

D

Ignition voltage is between 10volt and 16 volts.

D

No Crank DTCs set.

D

No EST DTCs.

Action Taken When the DTC Sets

D

The PCM will illuminate the malfunction indicator lamp
(MIL) the first time the fault is detected.

D

The PCM calculates an air flow value based on idle air
control valve position, throttle position, RPM and
barometric pressure.

D

The PCM will store condition which were present when
the DTC was set as Freeze Frame and in the Failure
Records data.

Conditions for Clearing the MIL/DTC

D

The PCM will turn the MIL “OFF” on the third
consecutive trip cycle during which the diagnostic has
been run and the fault condtion is no longer present.

D

A history DTC P0325 will clear after 40 cosecutive trip
cycle during which the warm up cycles have occurred
without a fault.

D

DTC P0325 can be cleared using the Tech2 “Clear
Info” function or by disconnecting the PCM battery
feed.

Diagnostic Aids

An intermittent may be caused by the following:

D

Poor connectons.

D

Mis routed harness.

D

Rubbed through wire insulation.

D

Broken wire inside the insulation.

Check for the following conditions:

D

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

D

Damaged harness-Inspect the wiring harness for
damage.

If the harness appears to be OK, observe the
Knock Present, Knock Sensor Noise Channel
display on the Tech 2 while moving connectors
and wiring harnesses related to the sensor.

6E–276

TROOPER 6VE1 3.5L ENGINE DRIVEABILITY AND EMISSIONS

A change in the display will indicate the location of
the fault.

If DTC P0325 cannot be duplicated, the
information included in the Faillure Records data
can be useful in determined vehicle mileage since
the DTC was last set.

If it is determined that the DTC occurs
intermittently, performing the DTC P0325
Diagnostic Chart may isolate the cause of the
fault.

DTC P0325 - ION Sensing Module Knock Intensity Circuit Fault

Step

Action

Value(s)

Yes

No

1

Was the “On-Board (OBD) System Check” performed?

—

Go to

Step 2

Go to

OBD

System

Check

2

1. Ignition “ON,” engine “OFF.”
2. Review and record Tech 2 Failure Records data.
3. Operate the vehicle within Failure Records

conditions as noted.

4. Using a Tech 2, monitor “DTC” info for DTC P0325.

Does the Tech 2 indicate DTC P0325 failed
thisignition?

—

Go to

Step 3

Refer to

Diagnostic

Aids

3

1. Ignition “OFF.”
2. Disconnect the ION sensing module.
3. Disconnect the PCM.

Is the action complete?

—

Go to

Step 4

—

4

Check the ION sensing harness between the PCM
(F68) and ION sensing module circuit (RED Wire) at
the KI line harness connector.

Was a problem found?

—

Verify repair

Go to

Step 5

5

1. Disconnect the ignition coil.

Is the action complete?

—

Go to

Step 6

—

6

Check the ION sensing harness between the ignition
coil and ION sensing module circuit at the DC motor
harness connector.

Was a problem found?

—

Verify repair

Go to

Step 7

7

Check the following items;

1. Ignition coil and ignition coil circuit.
2. Ignition coil ground circuit for a poor connection.
3. If a problem is found,repair wiring harness as

necessary.

Was a problem found?

—

Verify repair

Go to

Step 8

8

Replace the Ignition coil.

Is the action complete?

—

Verify repair

Go to

Step 9

9

Check the following items;

1. ION sensing module ground circuit for a poor

connection.

2. If a problem is found,repair wiring harness as

necessary.

Was a problem found?

—

Go to

Step 10

Go to

Step 11