2007 ISUZU KB P190 service

Engine Management – V6 – Diagnostics Page 6C1-2–152

Step Action Yes No
2 1 Switch off the ignition for 30 seconds.
2 Turn the ignition switch to the Start position or operate the vehicle within the conditions for running the DTC.
3 Using Tech 2, select the DTC display function.
Does DTC P0615, P0616 and P0617 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 Check for a fault condition in the following systems which can disable
the starting system:
• Starting System, refer to 6D1-2 Starting System – V6.
• Immobiliser System, refer to 11A Immobiliser.
W as any fault found and rectified? Go to Step 10 Go to Step 4
4 1 Remove the starter relay. Refer to 8A Electrical - Body and
Chassis.
2 Connect a test lamp between the ignition circuit of the starter relay and a good ground.
3 Switch on the ignition.
Does the test lamp illuminate when the ignition switch is turned to the
on position? Go to Step 5 Go to Step 6
5 1 Connect a test lamp between the control circuit of the starter
relay and a 12 V.
2 Turn the ignition switch to the Start position and then release it back to the on position.
Does the test lamp turn on when the ignition switch is turned to the
Start position and then turn off when the ignition switch returns to the
on position? Go to Step 8 Go to Step 7
6 Repair the ignition voltage circuit of the starter relay for a high
resistance or open circuit fault condition. Refer to 8A Electrical - Body
and Chassis for information on electrical wiring repair procedures.
W as the repair completed? Go to Step 10
—
7 Test the control circuit of the starter relay for a high resistance, open
circuit, short to ground or a short to voltage fault condition. Refer to
8A Electrical - Body and Chassis for information on electrical fault
diagnosis.
W as any fault found and rectified? Go to Step 10 Go to Step 9
8 Replace the starter relay. Refer to 8A Electrical - Body and Chassis.
W as the repair completed? Go to Step 10
—
9 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 10
—
10 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does the starter relay control circuit DTCs fail this ignition cycle? Go to Step 2 Go to Step 11
11 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK

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ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–154

• Refer to 6D1-1 Charging System – V6 for details of the charging system operation.
• Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
• To assist diagnosis, refer to 3 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
DTC P0625 or P0626 Diagnostic Table
Step Action Yes No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic
System Check in this Section
2 1 Switch off the ignition for 30 seconds.
2 Operate the vehicle within the conditions for running the DTC.
3 Using Tech 2, select the DTC display function.
Does DTC P0625 or P0626 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 Test the charging system for any fault condition that may cause
incorrect generator operation. Refer to 6D1-1 Charging System – V6.
W as any fault found and rectified? Go to Step 6 Go to Step 4
4 Test the Gen F signal circuit for a high resistance, open circuit, short
to ground or short to voltage fault condition. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
W as any fault found and rectified? Go to Step 6 Go to Step 5
5 Replace the ECM. Refer to Refer to 6C1-3 Engine Management – V6
– Service Operations.
W as the repair completed? Go to Step 7 —
6 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does any of the Generator F-terminal circuit DTCs fail this ignition
cycle? Go to Step 2 Go to Step 8
7 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.37 DTC P0627, P0628 or P0629
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0627 – Fuel Pump Relay Circuit Malfunction
• DTC P0628 – Fuel Pump Relay Voltage Low
• DTC P0629 – Fuel Pump Relay Voltage High

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ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–156

Step Action Yes
No
5 Repair the high resistance or open circuit fault condition in the ground
circuit of the fuel pump relay. Refer to 8A Electrical - Body and
Chassis for information on electrical wiring repair procedures.
W as the repair completed? Go to Step 9 —
6 Test the control circuit of the fuel pump relay for a high resistance,
open circuit, short to ground or a short to voltage fault condition. Refer
to 8A Electrical - Body and Chassis for information on electrical fault
diagnosis.
W as any fault found and rectified? Go to Step 9 Go to Step 8
7 Replace the fuel pump relay. Refer to 8A Electrical - Body and
Chassis.
W as the repair completed? Go to Step 9 —
8 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 9 —
9 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does the fuel pump relay control circuit DTCs fail this ignition cycle? Go to Step 2 Go to Step 10
10 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.38 DTC P0645, P0646 or P0647
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0645 – A/C Relay Circuit Malfunction.
• DTC P0646 – A/C Relay Voltage Low.
• DTC P0647 – A/C Relay Voltage High.
Circuit Description
The engine control relay applies battery voltage to the coil circuit of the air-conditioning (A/C) clutch relay through the
ignition circuit. Using a device called a driver, the ECM grounds control circuit of the A/C relay to activate the A/C clutch
and operate the A/C compressor. Refer to 2A Heater and Air-conditioning for details of the A/C compressor operation.
The driver has a feedback circuit that is pulled-up to a voltage. The ECM monitors the driver feedback circuit to
determine if the control circuit is open, shorted to ground or shorted to a positive voltage.
An A/C relay control circuit DTC sets if the ECM detects a fault condition in the A/C relay control circuit.
Conditions for Running the DTC
DTC P0645, P0646 or P0647 runs continuously once the following conditions are met:
• The ignition voltage is 10 – 16 V.
• The engine speed is greater than 80 rpm

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ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–158

Step Action Yes
No
5 1 Connect a test lamp between the control circuit of the A/C relay
and a 12 V.
2 Switch on the ignition with the engine not running.
3 Using Tech 2, command the A/C relay on and then off.
Does the test lamp turn on and off when the A/C relay is commanded
on and off? Go to Step 8 Go to Step 7
6 Repair the high resistance or open circuit fault condition in the ignition
voltage circuit of the A/C relay. Refer to 8A Electrical - Body and
Chassis for information on electrical wiring repair procedures.
W as the repair completed? Go to Step 10 —
7 Test the control circuit of the A/C relay for a high resistance, open
circuit, short to ground or short to voltage fault condition. Refer to 8A
Electrical - Body and Chassis for information on electrical fault
diagnosis.
W as any fault found and rectified? Go to Step 10 Go to Step 9
8 Replace the A/C relay. Refer to 8A Electrical - Body and Chassis.
W as the repair completed? Go to Step 10 —
9 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 10 —
10 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does any of the A/C relay control circuit DTCs fail this ignition cycle? Go to Step 2 Go to Step 11
11 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.39 DTC P0685, P0686 or P0687
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0685 – Engine Control Ignition Relay Circuit Malfunction
• DTC P0686 – Engine Control Ignition Relay Circuit Low Voltage
• DTC P0687 – Engine Control Ignition Relay Circuit High Voltage
Circuit Description
The supply voltage circuit of the engine control relay is directly connected to battery voltage. W hen the ignition switch is
turned on, the ECM grounds the relay control circuit to provide ignition voltage to various sensors and components that
controls the engine operation.
The ECM monitors the control circuit of the engine control relay for conditions that are incorrect for the commanded
state. An engine control relay circuit DTC sets if the ECM detects a fault condition in this circuit.

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Engine Management – V6 – Diagnostics Page 6C1-2–160

Step Action Yes
No
5 Repair the high resistance or open circuit fault condition in the battery
voltage circuit of the engine control relay. Refer to 8A Electrical -
Body and Chassis for information on electrical wiring repair
procedures.
W as the repair completed? Go to Step 9 —
6 Test the control circuit of the engine control relay for a high
resistance, open circuit, short to ground or a short to voltage fault
condition. Refer to 8A Electrical - Body and Chassis for information on
electrical fault diagnosis.
W as any fault found and rectified? Go to Step 9 Go to Step 8
7 Replace the engine control relay. Refer to 8A Electrical - Body and
Chassis.
W as the repair completed? Go to Step 9 —
8 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 9 —
9 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does the engine control relay control circuit DTCs fail this ignition
cycle? Go to Step 2 Go to Step 10
10 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.40 DTC P0700
DTC Descriptor
This diagnostic procedure supports DTC P0700 – Malfunction Indicator (MI) Request from Transmission Control Module
(TCM).
Circuit Description
The engine control module (ECM) communicates directly with the transmission control module (TCM) and other control
modules connected to the GM LAN serial data communication circuit through the GM LAN protocol.
DTC P0700 – Malfunction Indicator Request from TCM sets if the following condition exists:
• The TCM detects an emission related fault condition and sets a TCM DTC that represent the fault condition.
• The ECM receives a serial data signal from the TCM requesting the illumination of the malfunction indicator.
Conditions for Running the DTC
DTC P0700 runs continuously when the ignition is switched on.
Conditions for Setting the DTC
The ECM receives a serial data signal from the TCM requesting the illumination of the malfunction indicator lamp (MIL).

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ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–163

7 Test the control circuit of the cruise control clutch switch, which failed
for a high resistance, open circuit, short to ground or short to voltage
fault condition. Refer to 8A Electrical - Body and Chassis for
information on electrical fault diagnosis.
W as any fault found and rectified? Go to Step 9 Go to Step 8
8 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 9 —
9 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does DTC P0704 fail this ignition cycle? Go to Step 2 Go to Step 11
10 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.42 DTC P0850
DTC Descriptor
This diagnostic procedure supports DTC P0850 – Park / Neutral Signal Circuit Incorrect Signal.
Circuit Description
The Park / Neutral (P / N) switch is a part of the automatic transmission gear selector position switch assembly.
The P / N switch is a normally open switch that closes when the transmission is shifted to Park or Neutral position. The
ECM applies a reference 12 V to the signal circuit of the P / N switch when it is open. W hen the transmission is shifted
to the Park or Neutral position, the P / N switch closes and pulls the P/ N switch signal circuit to ground.
DTC P0850 sets when the ECM detects a fault condition in the P / N switch circuit.
Conditions for Running the DTC
DTC P0850 runs continuously when the ignition voltage is 10.0 – 16.0 V.
Conditions for Setting the DTC
DTC P0850 sets when the ECM detects one of the following fault conditions:
• The P / N switch signal circuit is pulled to ground for 100 seconds while the TCM sends a signal that the
transmission is in gear.
• The P / N switch signal circuit is 12 V for 100 seconds while the TCM sends a signal the transmission is in park or
neutral.
Conditions for Clearing the DTC
DTC P0850 is a Type ‘C’ DTC. Refer to 1.4 Diagnostic Trouble Codes in this Section, for action taken when Type ‘C’
DTCs set and conditions for clearing Type ‘C’ DTCs.
Additional Information
• The ECM uses the transmission range data to enable engine cranking when DTC P0850 sets.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• Refer to 6C1-1 Engine Management – V6 – General Information for details of the park / neutral switch operation.

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ISUZU KB P190 2007

Engine Management – V6 – Diagnostics Page 6C1-2–164

• Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
• To assist diagnosis, refer to 3 W iring Diagrams and Connector Charts in this Section, for the system wiring
diagram and connector charts.
DTC P0850 Diagnostic Table
Step Action Yes No
1 Has the Diagnostic System Check been performed?
Go to Step 2 Refer to
4.4 Diagnostic
System Check in this Section
2 1 Switch on the ignition.
2 Using Tech 2, observe the status of the automatic transmission gear position.
3 Shift the transmission lever across all gear levels.
Does Tech 2 display P/N when the transmission is in park or neutral
and In Gear when the transmission lever is in other positions? Go to Step 3 Go to Step 4
3
1 Switch off the ignition for 30 seconds.
2 Switch on the ignition.
3 Shift the transmission lever across all gear levels.
Does DTC P0850 fail this ignition cycle? Go to Step 4 Refer to Additional
Information in this DTC
4 1 Remove the transmission position switch wiring connector.
Refer to 7C4 Automatic Transmission_4L60E – On-vehicle
Servicing.
2 Connect a test lamp between the ground circuit of the transmission switch and a 12 V source.
Does the test lamp illuminate? Go to Step 5 Go to Step 6
5 1 Connect a 3 A jumper wire between the signal circuit of the
park / neutral signal circuit and a good ground.
2 Using Tech 2, observe the status of the transmission gear.
Does Tech 2 display a change from In Gear to P/N when the jumper
wire is connected? Go to Step 8 Go to Step 7
6 Repair the high resistance or open circuit fault condition in the ground
circuit of the transmission position switch. Refer to 8A Electrical -
Body and Chassis for information on electrical wiring repair
procedures.
W as the repair completed? Go to Step 10 —
7 Test the signal circuit of the park / neutral switch for a high resistance,
open circuit, short to ground or short to voltage fault condition. Refer
to 8A Electrical - Body and Chassis for information on electrical fault
diagnosis.
W as any fault found and rectified? Go to Step 10 Go to Step 9
8 Replace the transmission position switch. Refer to 7C4 Automatic
Transmission – 4L60E – On-vehicle Servicing.
W as the repair completed? Go to Step 10 —
9 Replace the ECM. Refer to 6C1-3 Engine Management – V6 –
Service Operations.
W as the repair completed? Go to Step 10 —

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Engine Management – V6 – Diagnostics Page 6C1-2–165

Step Action Yes
No
10 1 Using Tech 2, clear the DTCs.
2 Switch off the ignition for 30 seconds.
3 Start the engine.
4 Operate the vehicle within the conditions for running the DTC.
Does DTC P0850 fail this ignition cycle? Go to Step 2 Go to Step 11
11 Using Tech 2, select the DTC display function.
Does Tech 2 display any DTCs? Go to the
appropriate DTC
Table in this Section System OK
When all diagnosis and repairs are completed, check the system for correct operation.
7.43 DTC P1648
DTC Descriptor
This diagnostic procedure supports DTC P1648 – W rong Security Code Entered.
Circuit Description
Tech 2 is used to program the engine control module (ECM). Before any programming, a security code must be entered
into Tech 2. The ECM will check if the code entered is correct before continuing. If the security code is incorrect, DTC
P1648 sets.
Conditions for Running the DTC
Conditions for running the DTC are:
• The ignition is switched on.
• The ignition voltage is 10.0 – 16.0 V.
Conditions for Setting the DTC
An incorrect security code is entered into Tech 2 when attempting to program the ECM.
Action Taken When the DTC Sets
W hen the DTC sets, the malfunction indicator lamp (MIL) is not displayed.
Conditions for Clearing the DTC
The immobiliser security code is a Type ‘C’ DTC. Refer to 1.4 Diagnostic Trouble Codes in this Section, for action
taken when a Type ‘C’ DTC sets and conditions for clearing Type ‘C’ DTCs.
Additional Information
• Refer to 6C1-1 Engine Management –V6 – General Information for details of the ECM operation.
• Refer to 6C1-3 Engine Management –V6 – Service Operations for details on resetting the ECM.
• Since fault condition in a wiring connector may trigger DTCs, always test the connectors related to this diagnostic
procedure for shorted terminals or poor wiring connection before replacing any component. Refer to 8A Electrical -
Body and Chassis for information on electrical fault diagnosis.
• 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.

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ISUZU KB P190 2007