Circuit ISUZU KB P190 2007 Workshop Repair Manual

Engine Management – V6 – Diagnostics Page 6C1-2–20

• Ensure the resistance between the ECM housing and the battery negative cable is less than 0.5 Ω.
• Check the ECM bracket fasteners for correct torque value.
• Check all engine management related components for correct installation.
• Inspect the vacuum hoses for splits, kinks, oil contamination and proper connections, refer to the vehicle emission
control information label. Check the hoses thoroughly for any type of leak or restriction.
• Inspect the air intake ducts for being collapsed, split or for having damaged areas.
• Inspect for air leaks at the throttle body mounting area, mass air flow (MAF) sensor, intake manifold and intake
manifold sealing surfaces.
• Check for wiring harness routing that may be positioned too close to a high voltage or high current device such as
the following:
− Secondary ignition components, and
− Motors and generators.
NOTE
High voltage or high current devices may induce
electrical noise on a circuit, which can interfere
with normal circuit operation.
4.4 Diagnostic System Check
Description
The engine management diagnostic procedure is organised in a logical structure that begins with the Diagnostic System
Check. The Diagnostic System Check directs the diagnostic procedure to the logical steps necessary to diagnose an
engine driveability fault condition.
Test Description
The following numbers refer to the step numbers in the diagnostic table:
6 Tests the integrity of the GM LAN serial data communication circuit. A PIM DTC sets if the PIM detects a fault condition in the communication circuit. A fault condition on the serial data communication circuit may trigger
multiple DTCs on other sensors and components.
Step Action Yes No
1 Have you read the basic requirements?
Go to Step 2 Refer to
4.1 Basic
Requirements
2 Have you read the diagnostic precautions?
Go to Step 3 Refer to
4.2 Diagnostic Precautions
3 Have you performed the preliminary checks?
Go to Step 4 Refer to
4.3 Preliminary Checks
4 Using Tech 2, attempt to communicate with the PIM.
Does the PIM fail to communicate? Refer to 6E1
Powertrain Interface Module – V6 Go to Step 5
5 Does DTC B3902, C0550, U2100, U2105, U2106, P0633, or P1611
also set in the PIM? Refer to 6E1
Powertrain Interface Module – V6 Go to Step 6
6 Using Tech 2, view and record DTCs set at the ECM and TCM.
Does Tech 2 display any DTC? Go to Step 7 Refer to
5.1 Symptoms
Diagnosis Table

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Engine Management – V6 – Diagnostics Page 6C1-2–21

Step Action Yes No
7 Does Tech 2 display multiple DTCs?
Go to Step 8 Go to the diagnostic
table of the DTC
displayed. Refer to 7.1 DTC List
8 Does Tech 2 display any serial data communication circuit DTC? Go to the
appropriate serial
data communication circuit DTC table. Refer to
7.1 DTC List Go to Step 9
9 Does Tech 2 display any immobiliser circuit DTC? Go to the
appropriate
immobiliser circuit
DTC table. Refer to 7.1 DTC List Go to Step 10
10 Refer to the DTC Table of the fault condition that is most likely to
trigger multiple DTCs. Refer to 1.2 Diagnostic Trouble Code Tables
in this Section. — —
When all diagnosis and repairs are completed, check the system for correct operation.

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Engine Management – V6 – Diagnostics Page 6C1-2–23

• there is no Current DTC but a History DTC is stored.
Diagnostic Table
Checks Actions
Preliminary
• Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Gather information from the customer regarding the conditions that trigger the
intermittent fault such as:
• At what engine or ambient temperature range does the fault occur?
• Does the fault occur when operating aftermarket electrical equipment inside
the vehicle?
• Does the fault occur on rough roads or in wet road conditions?
• If the intermittent fault is a start and then stall condition, check the immobiliser
system. Refer to 11A Immobiliser.
Tech 2 Tests The following are lists of Tech 2 diagnostic tests that may be used to diagnose
intermittent faults:
• W riggle test the suspected wiring harness and connectors while observing Tech 2
operating parameters. If Tech 2 read-out fluctuates during this procedure, check
the tested wiring harness circuit for a loose connection.
• Observe the freeze frame / failure records for the suspected history DTC and then
operate the vehicle in the conditions that triggers the intermittent fault while an
assistant observes the suspected Tech 2 operating parameter data.
• Capture and store data in the snapshot mode when the fault occurs. The stored
data may be played back at a slower rate to aid diagnostics. Refer to Tech 2 User
Instructions for further information on the Snapshot function.
• Compare the engine operating parameters of the engine being diagnosed to the
engine operating parameters of a known good engine.
Malfunction Indicator Lamp The following conditions may cause an intermittent Malfunction Indicator Lamp fault with no DTC listed:
• Electromagnetic interference (EMI) caused by a faulty relay, ECM controlled
solenoid, switch or other external source.
• Incorrect installation of aftermarket electrical equipment such as the following:
• mobile phones,
• lights, or
• radio equipment.
• ECM grounds are loose.

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Engine Management – V6 – Diagnostics Page 6C1-2–24

Checks Actions
Temperature Related Temperature related intermittent fault condition occurs only when the engine or ambient
temperature is hot, or only when it is cold.
• If the intermittent fault is heat related, review Tech 2 data in relationship to the
following:
• high ambient temperature,
• engine generated heat,
• circuit generated heat due to a poor electrical connection or high electrical
load, and
• higher than normal load conditions (towing, etc.).
• If the intermittent fault is related to cold ambient or engine temperature, review
Tech 2 data in relationship to the following:
• low ambient temperature, and
• the fault condition that occurs only on a cold start situation.
Additional Tests
• Incorrect installation of aftermarket electrical equipment such as the following:
• mobile phones,
• theft deterrent alarms,
• lights, or
• radio equipment.
• Electromagnetic interference (EMI) caused by a faulty relay, ECM controlled
solenoid or switch. The fault is triggered when the relay or solenoid is activated.
• Test the A/C compressor clutch and some relays that contain a clamping diode or
resistor for an open circuit.
• Test the generator for a faulty rectifier bridge that may allow the A/C noise into the
ECM electrical circuit.
When all diagnosis and repairs are completed, check the system for correct operation.
5.3 Backfire
Description
The air / fuel mixture in the intake manifold or in the exhaust system ignites which produces a loud popping noise.
Checks Actions
Preliminary Perform the Preliminary Checks. Refer to 4.3 Preliminary Checks in this
Section.
Sensor / System • Check the air intake system and crankcase for air leaks.
• Check the PCV System for correct operation. Refer to 6A1 Engine Mechanical –
V6.
• Use Tech 2 to monitor the knock sensor system for excessive spark retard
activity. Check for items that cause spark retard activity.

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Engine Management – V6 – Diagnostics Page 6C1-2–25

Checks Actions
Fuel System
• Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6 – V6.
• restricted fuel filter,
• incorrect fuel pressure, and
• contaminated fuel.
• Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management –
V6 – Service Operations.
• Perform the fuel injector balance test, refer to 6.3 Fuel Injector Balance
Test in this Section.
• Check the items that can cause an engine to run lean.
• Check the items that cause an engine to run rich.
Ignition System
• Check for an intermittent ignition circuit malfunction.
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil ground circuit.
Engine Cooling System Check the engine for over-heating. Refer to 6B1 Engine Cooling – V6.
Engine Mechanical Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical – V6.
• low compression, and
• worn valve train components.
Additional Checks
• Check the exhaust system for possible restrictions. Refer to 6F Exhaust System –
V6.
• Electromagnetic interference (EMI) on the crankshaft position (CKP) sensor can
cause an engine misfire condition.
Using Tech 2, monitor the engine speed parameter. A sudden increase in the engine speed parameters without moving the throttle position indicates that an
Electromagnetic Interference fault may be present.
W iring harness routing which may be positioned very close to a high voltage or high current device such as the following may induce EMI:
• secondary ignition components, or
• motors and generators.
Dirty starter motor commutator or brushes can mask the crankshaft position sensor signal.
• Check the torque converter clutch (TCC) operation. A TCC that applies too soon
can cause engine detonation, which will trigger spark retard activity. Refer to 7C1
Automatic Transmission – 4L60E – General Information.
When all diagnosis and repairs are completed, check the system for correct operation.

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Engine Management – V6 – Diagnostics Page 6C1-2–26

5.4 Cranks But Does Not Run
Definition
The engine cranks normally but does not start.
Checks Actions
Preliminary • Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Check the immobiliser system for correct operation. Refer to 11A Immobiliser.
Sensor / System
• Check the engine coolant temperature (ECT) sensor for an incorrect value.
Compare the engine coolant temperature against the intake air temperature (IAT)
on a cold engine. The ECT and IAT sensor values should be within ± 3°C of each
other. Refer to 6C1-3 Engine Management – V6 – Service Operations for details
of the Temperature vs. Resistance Table.
• Check the mass air flow (MAF) sensor installation. Incorrect installation of the
MAF sensor may cause hard start condition. Refer to 6C1-3 Engine Management
– V6 – Service Operations.
• Check for a dirty starter motor commutator or brushes that can mask the
crankshaft position sensor signal.
Fuel System • Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.
• restricted fuel filter,
• incorrect fuel pressure,
• contaminated fuel, and
• incorrect fuel pump relay operation.
• Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management –
V6 – Service Operations.
Ignition System • Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
Check for loose ignition coil ground circuit.
Engine Mechanical • Check for excessive oil in combustion chamber. Refer to 6A1 Engine Mechanical
– V6.
• Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical –
V6.
• low compression, and
• worn valve train components.
When all diagnosis and repairs are completed, check the system for correct operation.

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Engine Management – V6 – Diagnostics Page 6C1-2–30

Checks Actions
Ignition System
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil ground circuit.
Engine Mechanical
• Check for excessive oil in combustion chamber. Refer to 6A1 Engine Mechanical
– V6.
• Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical –
V6.
• low compression, and
• worn valve train components.
When all diagnosis and repairs are completed, check the system for correct operation.
5.9 Hesitation, Sag and Stumble
Description
Momentary lack of response or hesitation as the accelerator is depressed. This condition is usually more severe when
first trying to make the vehicle move from a standing start but can occur at any vehicle speed.
Checks Actions
Preliminary • Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Check the air filter element and intake air ducts for blockages.
Sensor / System
• Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters.
The HO2s should respond quickly to different throttle positions.
• Inspect the accelerator pedal position (APP) sensor harness connector for correct
connection. Poor connection of this connector will not set a DTC.
Fuel System • Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.
• restricted fuel filter,
• incorrect fuel pressure, and
• contaminated fuel.
• Check the operation of the fuel injectors. Refer to 6C Fuel System – V6.
• Perform the fuel injector balance test, refer to 6.3 Fuel Injector Balance
Test in this Section.
• Check for fault conditions that cause an engine to run rich or to run lean.

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Engine Management – V6 – Diagnostics Page 6C1-2–31

Checks Actions
Ignition System
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil ground circuit.
Engine Cooling System Check the engine thermostat for correct operation and heat range. Refer to 6B1 Engine
Cooling – V6.
Additional Checks • Check the generator output voltage. Refer to 6D1-1 Charging System – V6.
When all diagnosis and repairs are completed, check the system for correct operation.
5.10 Lack of Power, Sluggishness or
Sponginess
Description
The engine delivers less than normal power. There is little or no increase in vehicle speed when the accelerator pedal is
partially depressed.
Checks Actions
Preliminary • Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Check the air filter element and intake air ducts for blockages.
Sensor / System
• Use Tech 2 to monitor the knock sensor system for excessive spark retard
activity. Check for items that cause spark retard activity.
• Inspect the accelerator pedal position (APP) sensor harness connector for correct
connection. Poor connection of this connector will not set a DTC.
Fuel System • Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.
• restricted fuel filter,
• incorrect fuel pressure, and
• contaminated fuel.
• Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management –
V6 – Service Operations.
• Perform the fuel injector balance test, refer to 6.3 Fuel Injector Balance
Test in this Section.
• Check for fault conditions that can cause the engine to run rich or run lean.

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Engine Management – V6 – Diagnostics Page 6C1-2–32

Checks Actions
Ignition System
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs, refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil ground circuit.
Engine Mechanical
• Check for the following engine mechanical fault condition. Refer to 6A1 Engine
Mechanical – V6.
• low engine compression, and
• worn valve train components.
Additional Checks
• Check the exhaust system for possible restrictions. Refer to 6F Exhaust System –
V6.
• Test for other TCM related faults that may cause the transmission to operate in
the default mode.
• Check for transmission mechanical faults that may produce similar symptoms
such as slipping clutch.
When all diagnosis and repairs are completed, check the system for correct operation.
5.11 Poor Fuel Economy
Description
As confirmed by an actual road test, the fuel economy as compared to the previous fuel consumption of the same
vehicle is noticeably lower.
Checks Actions
Preliminary • Perform the preliminary checks. Refer to 4.3 Preliminary Checks in this
Section.
• Check the air filter element and intake air ducts for blockages.
• Check for correct tyre pressure. Refer to the Owners Manual.
• Check the recent driving conditions are the same compared to the previous when
the fuel consumption is normal. The following are list of driving conditions that
may affect fuel consumption:
− vehicle load,
− acceleration rate,
− A/C or other electrical equipment use, and
− vehicle used for towing.

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Engine Management – V6 – Diagnostics Page 6C1-2–33

Checks Actions
Sensor / System
• Check the air intake system and crankcase for air leaks.
• Check the PCV System for correct operation. Refer to 6A1 Engine Mechanical –
V6.
• Check for the correct calibration of the speedometer. Refer to 8A Electrical-Body.
• Use Tech 2 to monitor the knock sensor system for excessive spark retard
activity. Check for items that cause spark retard activity.
• Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters.
The HO2s should respond quickly to different throttle positions.
Fuel System • Check the fuel system for the following fault conditions. Refer to 6C Fuel System
– V6.
− restricted fuel filter,
− incorrect fuel pressure, and
− contaminated fuel.
• Check the operation of the fuel injectors. Refer to 6C1-3 Engine Management –
V6 – Service Operations.
• Perform the fuel injector balance test, refer to 6.3 Fuel Injector Balance
Test in this Section.
• Check the items that cause an engine to run rich.
• Check for foreign material accumulation in the throttle bore, carbon build-up on
the throttle valve or on the throttle shaft.
• Check the throttle body for tampering.
Ignition System
• Inspect for moisture or corrosion around the spark plug / ignition coil area.
• Test the ignition coil voltage output. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Remove and inspect the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
NOTE
If the spark plugs are fouled, determine the cause of the fouling before
replacing the spark plugs. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
• Check for loose ignition coil ground circuit.
Engine Cooling System
• Check the engine thermostat for proper operation and correct heat range. Refer to
6B1 Engine Cooling – V6.
Engine Mechanical Check for the following engine fault conditions. Refer to 6A1 Engine Mechanical – V6.
• low compression, and
• worn valve train components.

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