Circuit ISUZU KB P190 2007 Workshop Repair Manual

Engine Management – V6 – Diagnostics Page 6C1-2–153

Step Action Yes No
When all diagnosis and repairs are completed, check the system for correct operation.
7.36 DTC P0625 or P0626
DTC Descriptors
This diagnostic procedure supports the following DTCs:
• DTC P0625 – Alternator F Terminal Low Voltage
• DTC P0626 – Alternator F Terminal High Voltage
Circuit Description
The voltage regulator within the generator regulates the generator charge output by increasing or decreasing the
generator on time. The generator field (Gen F) duty cycle output signal represents the generator on time. Refer to 6D1-1
Charging System – V6 for details of the charging system operation.
The ECM monitors the Gen F terminal output signal to calculate Gen F duty cycle percentage. This enables the ECM to
provide engine idle compensation based on electrical loads and to detect a fault condition in the generator operation.
A Generator F-terminal circuit DTC sets if the ECM detects the Gen F duty cycle is outside the specified range for a
predetermined set of parameters.
Conditions for Running the DTC
DTC P0625
Runs continuously when the following conditions are met:
• There is no generator, CKP sensor or CMP sensor DTC set.
• The engine speed is less than 3000 rpm
• The generator is not commanded off.
DTC P0626
Runs continuously when the following conditions are met:
• There is no generator, CKP sensor or CMP sensor DTC set.
• The ignition is switched on with the engine not running
Conditions for Setting the DTC
DTC P0625
The ECM detects the Gen F Terminal Signal parameter is less than five percent for 15 seconds.
DTC P0626
The ECM detects the Gen F Terminal Signal parameter is greater than five percent for 15 seconds.
Conditions for Clearing DTC
The Generator F-terminal circuit are Type C DTCs. 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
• 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 ECM operation.

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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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Engine Management – V6 – Diagnostics Page 6C1-2–155

Circuit Description
The ground circuit of the fuel pump relay coil is directly connected to ground. W hen the ignition switch is turned on and
all the conditions required to enable fuel pump operation are met, the ECM applies battery voltage to the fuel pump relay
control circuit to operate the fuel pump. Refer to 6C Fuel System – V6 for further information.
The ECM monitors the control circuit of the fuel pump relay for conditions that are incorrect for the commanded state. A
fuel pump relay control circuit DTC sets if the ECM detects a fault condition in this circuit.
Conditions for Running the DTC
Run continuously once the following conditions are met:
• the ignition is switched on, and
• the ignition voltage is 10.0 – 16.0 V.
Conditions for Setting the DTC
The ECM detects a condition that are incorrect for the fuel pump relay commanded state.
Conditions for Clearing the DTC
The fuel pump relay control circuit DTCs are Type C DTCs. 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
• Refer to 6C Fuel System – V6 for details of the fuel pump operation.
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• 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 P0627 to P0629 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 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 P0627, P0628 and P0629 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 1 Remove the fuel pump relay. Refer to 8A Electrical - Body and
Chassis.
2 Connect a test lamp between the ground circuit of the fuel pump relay and a 12 V.
Does the test lamp illuminate? Go to Step 4 Go to Step 5
4 1 Connect a test lamp between the control circuit and ground
circuit of the fuel pump relay.
2 Using Tech 2, command the fuel pump relay on.
Does the test lamp switch from off to on as Tech 2 commands the fuel
pump relay from off to on? Go to Step 7 Go to Step 6

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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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Conditions for Setting the DTC
Conditions for Setting DTC P0645
The ECM detects an open circuit fault condition in the A/C relay control circuit.
Conditions for Setting DTC P0646
The ECM detects a short to ground fault condition in the A/C relay control circuit.
Conditions for Setting DTC P0647
The ECM detects a short to voltage fault condition in the A/C relay control circuit.
Conditions for Clearing the DTC
The A/C relay control circuit DTCs are Type C DTCs. 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
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• Refer to 2A Heater and Air-conditioning for details of the A/C system operation.
• Since a 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.
Test Description
The following number refers to the step numbers in the diagnostic table:
3 A fault condition in the HVAC system may trigger this DTC.
DTC P0645, P0646 or P0647 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 Switch on the A/C system or operate the vehicle within the conditions for running the DTC.
3 Using Tech 2, select the DTC display function.
Does DTC P0645 P0646 or P0647 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 Check for a fault condition in the HVAC system, which can disable the
AC compressor clutch. Refer to 2A Heater and Air-conditioning for
details of the A/C compressor operation.
W as any fault found and rectified? Go to Step 10 Go to Step 4
4 1 Remove the A/C relay. Refer to 8A Electrical - Body and
Chassis.
2 Connect a test lamp between the ignition circuit of the A/C relay coil and the ECM housing.
3 Switch on the ignition with the engine not running.
Does the test lamp illuminate? Go to Step 5 Go to Step 6

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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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Conditions for Running the DTC
DTCs P0685, P0686 and P0687 run continuously once the following conditions are met:
• The ignition is switched on
• The ignition voltage is 10.0 – 16.0 V.
Conditions for Setting the DTC
The ECM detects a condition that is incorrect for the engine control relay commanded state.
Conditions for Clearing the DTC
The engine control relay control circuit DTCs are Type C DTCs. 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
• For an intermittent fault condition, refer to 5.2 Intermittent Fault Conditions in this Section.
• 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.
Test Description
The following number refers to the step number in the diagnostic table:
4 Removal of the ECM Fuse 29 enables the ECM to power down completely prior to the test procedure.
DTC P0685, P0686 or P0687 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 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 P0685, P0686 and P0687 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 1 Remove the engine control relay. Refer to 8A Electrical - Body
and Chassis.
2 Connect a test lamp between the battery voltage circuit of the engine control relay and a good ground.
Does the test lamp illuminate? Go to Step 4 Go to Step 5
4 1 Switch off the ignition.
2 Remove and reinstall the ECM fuse 29 from the engine compartment fuse and relay panel assembly.
3 Connect a test lamp between the control circuit and the battery voltage circuit of the engine control relay.
4 Switch on the ignition.
Does the test lamp switches from off to on when the ignition switch is
turned form off to on? Go to Step 7 Go to Step 6

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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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Conditions for Clearing the DTC
DTC P0700 – Malfunction Indicator Request from TCM is a Type A DTCs. Refer to 1.4 Diagnostic Trouble Codes in
this Section, for action taken when a Type A DTC sets and conditions for clearing Type A DTCs.
Additional Information
• Refer to 6C1-1 Engine Management – V6 – General Information for details of the ECM operation.
• 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 Secion, for the system wiring
diagram and connector charts.
DTC P0700 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 P0700 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 Are other powertrain DTCs also set?
Go to the
appropriate DTC
Table in this Section Refer to 7C2
Automatic
Transmission –
4L60E – Electrical Diagnosis
When all diagnosis and repairs are completed, check the system for correct operation.
7.41 DTC P0704
DTC Descriptor
This diagnostic procedure supports DTC P0704 – Clutch Switch Input Circuit Malfunction.
Circuit Description
The clutch pedal switch disengages the cruise control when the clutch is depressed, in much the same way that the
brake pedal switch is used to disengage the cruise control feature.
The cruise control cancel switch is normally closed when the clutch pedal is at rest, opening when the pedal is pressed.
Activation of this switch removes the signal to the ECM which will then deactivate the cruise control.
Conditions for Running the DTC
Runs continuously when the ignition is switched and the engine is running.
Conditions for Setting the DTC
The ECM detects 15 gear changes with less than three clutch switch inputs.
NOTE
The ECM determines that a gear change has
been performed by the engine speed / vehicle
speed ratio.

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Conditions for Clearing the DTC
The clutch switch circuit DTC 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
• 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 clutch switch operation.
• Refer to 8C Cruise Control for clutch pedal switch operation and testing.
• 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 P0704 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 P0704 fail this ignition cycle? Go to Step 3 Refer to Additional
Information in this DTC
3 1 Switch on the ignition with the engine not running.
2 On Tech 2 select: Engine / V6 Engine / Data Display / Engine
Data 1 .
3 Observe the status of the cruise control cancel switch.
4 Depress the clutch pedal.
Does Tech 2 display change from Inactive to Active when the pedal is
pressed? Refer to Additional
Information in this DTC Go to Step 4
4 1 Disconnect the wiring connector from the cruise control cancel
switch. Refer to 8C Cruise Control – HFV6.
2 Switch on the ignition.
3 Connect a test lamp between the voltage circuit of cruise control cancel clutch switch and a ground.
Does the test lamp illuminate? Go to Step 6 Go to Step 5
5 Repair the high resistance or open circuit fault condition in the voltage
circuit of the clutch switch. 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 cruise control cancel clutch switch. Refer to 8C Cruise
Control – HFV6.
W as any fault found and rectified? Go to Step 9 Go to Step 7

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