DTC CHECK ISUZU KB P190 2007 Workshop Repair Manual

Engine Management – V6 – Diagnostics Page 6C1-2–5

• fuel trim DTCs, or
• catalyst DTCs.
1.3 Symptoms Diagnostics
The Diagnostic System Check directs the service technician to the symptoms diagnostics if the following conditions
exist:
• a vehicle driveability fault condition exists,
• there is no current diagnostic trouble code presently stored in the ECM, and
• all Tech 2 engine data parameters are within normal operating range.
1.4 Diagnostic Trouble Codes
The ECM constantly performs self-diagnostic tests on the engine management system. W hen the ECM detects a fault
condition in the engine operating parameters, the ECM sets a diagnostic trouble code (DTC) to represent that fault
condition. The following are the types of DTCs programmed in the ECM. In addition, DTCs are classified as either a
current or history DTC.
• Type A – emission related DTCs,
• Type B – emission related DTCs, and
• Type C – non-emission related DTCs.
NOTE
Depending on the type of DTC set, the ECM may
command the malfunction indicator lamp (MIL) to
illuminate and warn the driver there is a fault in
the engine management system.
Type A – Emission Related DTCs
The ECM takes the following action when a Type A DTC runs and fails:
• sets a current Type A DTC that represents the fault condition,
• illuminates the instrument cluster malfunction indicator lamp (MIL), and
• records the operating condition at the time the diagnostic fails and stores this information in the freeze frame
failure record.
Type B – Emission Related DTCs
The ECM takes the following action when a Type B DTC runs and fails:
• On the first time a Type B DTC fails, the ECM takes the following actions:
− sets a current Type B DTC that represents the fault condition, and
− records the operating conditions at the time the fault sets and stores this information in the failure records.
• On the second consecutive ignition cycle that a Type B DTC fails, the ECM takes the following actions:
− activates the instrument cluster malfunction indicator lamp (MIL), and
− records the operating condition at the time the diagnostic fails and stores this information in the freeze frame
failure record.
Conditions for Clearing Type A or Type B DTCs
• The current DTC clears when there is no fault condition in the current ECM self-diagnostics.
• If there are no DTCs logged after three or four consecutive ignition cycles, the ECM deactivates the instrument
cluster malfunction indicator lamp (MIL).
• Type A or Type B History DTC clears when there is no fault condition after 40 consecutive warm-up cycles.

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Engine Management – V6 – Diagnostics Page 6C1-2–19

• Do not start the engine if the battery terminal is not properly secured to the battery.
• Do not disconnect or reconnect the following while the ignition is switched on or when the engine is running:
− Any engine management system component electrical wiring connector, or
− Battery terminal leads.
• Ensure the correct procedure for disconnecting and connecting engine management system electrical wiring
connectors is always followed. For information on the correct procedure for disconnecting and connecting specific
wiring connectors, refer to 6C1-3 Engine Management – V6 – Service Operations.
• Ensure that all wiring harness connectors are fitted correctly.
• W hen steam or pressure cleaning engines, do not direct the cleaning nozzle at engine management system
components.
• Do not clear any DTCs unless instructed.
• The fault must be present when using the diagnostic trouble code (DTC) diagnostic tables. Otherwise,
misdiagnosis or replacement of good parts may occur.
• Do not touch the ECM connector pins or soldered components on the ECM circuit board to prevent ECM
Electrostatic Discharge damage. Refer to 8A Electrical - Body and Chassis for information on Electrostatic
Discharge.
• Use only the test equipment specified in the diagnostic tables as other test equipment may give incorrect results or
damage good components.
• The ECM is designed to withstand normal current draw associated with vehicle operations. However, the following
fault conditions or incorrect test procedure may overload the ECM internal circuit and damage the ECM:
− A short to voltage fault condition in any of the ECM low reference circuits may cause internal ECM and / or
sensor damage. Therefore, any short to voltage fault condition in the ECM low reference circuits must be
rectified before replacing a faulty component.
− A short to ground fault condition in any of the ECM 5 V reference circuits may cause internal ECM and / or
sensor damage. Therefore, any short to ground fault condition in the ECM 5 V reference circuits must be
rectified before replacing a faulty component.
− W hen using a test lamp to test an electrical circuit, do not use any of the ECM low reference circuits or 5 V
reference circuits as a reference point. Otherwise, excessive current draw from the test lamp may damage
the ECM.
• Disregard DTCs that set while performing the following diagnostic Steps:
− Using Tech 2 actuator tests, or
− Disconnecting an engine management system sensor connector then switching on the ignition.
• After completing the required diagnostics and service operations, road test the vehicle to ensure correct engine
management system operation.
4.3 Preliminary Checks
The preliminary checks are a set of visual and physical checks or inspections that may quickly identify engine
management system fault condition.
• Refer to the appropriate Service Techlines for relevant information regarding the fault condition.
• Ensure the battery is fully charged.
• Inspect the battery connections for corrosion or a loose terminal.
• Ensure that all engine management system related fuses are serviceable.
• Inspect for incorrect aftermarket theft deterrent devices, lights or mobile phone installation.
• Ensure there is no speaker magnet positioned too close to any electronic module that contains relays.
• Inspect the engine wiring harness for proper connections, pinches or cuts.
• Ensure that all engine management related electrical wiring connectors are fitted correctly.
• Inspect the ECM ground connections for corrosion, loose terminal or incorrect position.

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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 6C1-2–27

5.5 Cuts Out, Misses
Description
Steady pulsation or jerking that is usually more severe as the engine load increases. This condition is not normally felt
greater than 1500 rpm or 48 km/h. The exhaust has a steady spitting sound at idle or low 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.
• Check for intake manifold vacuum leak.
Sensor / System
• Using Tech 2, check the heated oxygen sensor (HO2s) operating parameters.
The HO2s should respond quickly to different throttle positions.
• Use Tech 2 to monitor the knock sensor system for excessive spark retard
activity. Check for items that cause spark retard activity. Refer to 7.19 DTC
P0327, P0328, P0332 or P0333.
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 cause an engine to run rich or to run lean.
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 grounds.
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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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 6C1-2–37

6 Functional Checks
6.1 General Information
The items detailed in the following pages are to be used when there is a customer complaint and there are no diagnostic
trouble codes set, or one or more of the Tech 2 data values are not within the typical values. They are also to be used
when instructed from a DTC table. Before using these tables, you should refer to 5 Symptoms Diagnostics in this
Section, which may direct you to using the following functional checks.
The purpose of these tables is to diagnose engine control module (ECM) controlled components or sub-systems that do
not have diagnostic trouble codes assigned to them. Another purpose of these tables is for Technicians who feel
confident that a particular part of the sub-system is not operating properly and wants only to check that particular item
for proper operation without going through lengthy diagnostic procedures.
6.2 Fuel Injector Coil Test
The fuel injector coil test is divided into two parts. Begin by performing the fuel injector coil quick test. Then only perform
the Injector Coil Test – W ith Special Tool J39021 procedure if the quick test determines that there is a faulty fuel injector.
Fuel Injector Coil Quick Test
Test Description
The following numbers refer to the step numbers in the diagnostic table:
1 This step checks if the engine coolant temperature is within the correct range.
2 This step tests each fuel injector resistance within a specific temperature range.
3 This step determines if all of the fuel injectors are within 3 ohms of each other.
Step Action Value(s) Yes No
1 Using Tech 2, observe the engine coolant temperature
(ECT).
Is the ECT within the specified range? 10 – 32 °C Go to Step 2 Go to Step 3
2 1 Disconnect the fuel injector harness connector,
refer to 2.13 Fuel Rail Assembly, in 6C1-3 Engine
Management – V6 – Service Operations.
2 Using a digital ohmmeter and connector test adaptor kit J 35616-A, measure the resistance of
each fuel injector between the ignition voltage
circuit and the fuel injector control circuit. Refer to
8A Electrical - Body and Chassis for information
on testing for continuity and to Figure 6C1-2 – 9
and Figure 6C1-2 – 10 for the fuel injector
harness connector.
Do any of the fuel injectors display a resistance outside
the specified range? 11 – 14 ΩRefer to Injector
Coil Test – W ith
Special Tool J39021 in this Section Injectors OK

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Engine Management – V6 – Diagnostics Page 6C1-2–48

Additional Information
• Use the J 35616-B Connector Test Adapter Kit for any test that requires probing the ECM harness connector or a
component harness connector.
• Inspect the ignition coils for aftermarket devices. An aftermarket device connected to the ignition coil circuits, may
cause a condition with the ignition coils.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• To assist diagnosis, refer to 3 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
4 The ignition coils for each bank are fused separately. If a fuse opens or the ignition 1 voltage circuit opens between the fuse and the splice, all the ignition coils for one bank of the engine would be inoperative. If the ground
circuit opens at the engine block, the ignition coils would be inoperative for one bank of the engine.
5 This step tests for an open or a high resistance in the ignition 1 voltage circuit of the ignition coil. If the DMM does not display near battery voltage there is an open or a high resistance in the circuit.
6 This step determines if the ground circuit is open. If the circuit is open, the ignition coils would be inoperative for one bank of the engine.
7 This step determines if the ignition 1 voltage circuit is shorted to ground. If the fuse is open, the ignition coils would be inoperative for one bank of the engine.
Diagnostic Table
Step Action Value(s) Yes No
1
Has the Diagnostic System Check been performed? —
Go to Step 2 Refer to
4.4 Diagnostic System Check
2 W ere you sent here from DTC P0300 or P0301-P0306? —
Go to Step 3 Go to DTC P0300 or
DTC P0301 – P0306
3 1 Start the engine.
2 Allow the engine to reach operating temperature.
3 Operate the engine at 2,000 rpm.
4 Monitor all of the Misfire Current Counters with a scan tool. There are a total of 6 counters,
1 counter per cylinder.
Are any of the Misfire Current Counters incrementing? —
Go to Step 4 Go to
5.2 Intermittent Fault Conditions
4 Are all the misfire counters incrementing for one bank
of the engine? —
Go to Step 7 Go to Step 5
5 1 Ignition OFF.
2 Disconnect the appropriate ignition coil.
3 Ignition ON, engine OFF.
4 Connect a test lamp between the battery voltage circuit of the ignition coil and a good ground.
5 Measure the voltage between the probe of the test lamp and a good ground with a DMM. Refer
to 8A Electrical - Body and Chassis for the
procedure to measure voltage drop.
Is the voltage at the specified value? B+
Go to Step 6 Go to Step 9

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