Page 857 of 5267

When Monitored:
Ignition on.
Set Condition:
Low voltage detected at the WIF signal circuit at the ECM.
Possible Causes
OTHER DTC’S PRESENT
WATER IN FUEL
ECM
INTERMITTENT CONDITION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.OTHER DTC’S PRESENT
With the scan tool, read DTCs.
Do you have any additional water in fuel DTC’s?
Ye s>>
Repair other Water in fuel sensor DTC’s first.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 2
2.WAT E R I N F U E L
Using the service publications as a guide, drain the water in fuel separator.
Did the DTC become inactive after draining the water in fuel separator?
Ye s>>
Clear DTC, repair complete.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 3
3.ECM
Disconnect the WIF sensor harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Using the scan tool, monitor for DTC’s while connecting a jumper wire
between the (G123) signal circuit of the water in fuel sensor and battery
voltage.
Did the water in fuel light go out?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diag-
nostic Procedure). (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)
No>>
Replace and program the ECM in accordance with the Ser-
vice Information.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 860 of 5267

4.HIGH RESISTANCE IN THE GROUND CIRCUIT
Measure the voltage between the generator case and the B- post of the battery.
Is the voltage above .1 volts?
Ye s>>
Repair the high resistance in the ground circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 5
5.GENERATOR
Disconnect the Generator field harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the generator field terminals.
Is the resistance between .5 and 15 Ohms?
Ye s>>
Go To 6
No>>
Replace the generator.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
6.All
Turn the ignition off.
Reconnect the Generator field harness connector.
Disconnect the ECM harness connectors.
NOTE: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
Measure and record the voltage between battery positive circuits of the
ECM harness connector and the battery negative circuits of the ECM
harness connector.
Turn the ignition off.
Reconnect the ECM harness connectors.
Start the engine.
Use the scan tool to measure and record battery voltage.
Compare the voltage reading from the voltmeter with that of the scan
tool.
Are the readings within 3 volts of each other?
Ye s>>
Te s t C o m p l e t e .
No>>
Replace and program the ECM in accordance with the Service Information.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 870 of 5267

3.OPEN FUSED B+ TO ECM
Turn the ignition off.
Disconnect the ECM harness connectors.
Turn the ignition on.
Measure the resistance between the positive battery post and the ECM
supply circuits.
Is the resistance less than 10 Ohms?
Ye s>>
Go To 4
No>>
Repair the open fused B+ circuit to ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
4.OPEN GROUND CIRCUIT
Measure the resistance between the negative battery post and the ECM
ground circuits.
Is the resistance less than 10 Ohms?
Ye s>>
Go To 5
No>>
Repair the open ground circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
5.BATTERY + SHORTED TO OTHER CIRCUITS
Measure the resistance between the ECM supply circuits and all other
circuits in the ECM harness connector, except other supply circuits.
Is the resistance greater than 100k Ohms?
Ye s>>
Go To 6
No>>
Repair the battery circuit short to other circuits in engine
harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 873 of 5267

When Monitored:
When the ignition is on.
Set Condition:
When the signal from the #2 intake air heater output does not match the signal from the #2 intake air heater
feedback.
Possible Causes
LOOSE CONNECTION
INTAKEAIRHEATERRELAY
SIGNAL CIRCUIT OPEN FROM RELAY TO ECM
SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE
ECM
INTERMITTENT CONDITION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.RELAY CLICKING
Ignition on, engine not running.
With the scan tool, actuate the #1 Intake Air Heater.
Can you hear the Relay clicking?
Ye s>>
Go To 2
No>>
Go To 3
2.LOOSE CONNECTION
While the relay is clicking , wiggle the wiring harness and connectors.
Does this interrupt the clicking?
Ye s>>
Repair the poor connection.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 3
3.INTAKE AIR HEATER RELAY
Turn the ignition off.
Remove the Intake Air Heater #1 Relay.
Check connectors - Clean/repair as necessary.
Measure the resistance between the signal and return posts of the intake air heater relay.
Is the resistance between 15 and 25 Ohms?
Ye s>>
Go To 4
No>>
Replace the Intake Air Heater #1 relay.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 874 of 5267

4.SIGNAL CIRCUIT OPEN FROM RELAY TO ECM
Disconnect the ECM harness connectors.
Check connectors - Clean/repair as necessary.
Measure the resistance of the intake air heater relay signal circuit between the ECM connector and the intake air
heater relay connector.
Is the resistance less than 10 Ohms?
Ye s>>
Go To 5
No>>
Repair the open signal circuit from PDC to ECM harness connector.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
5.RETURN CIRCUIT SHORTED TO BATTERY NEGATIVE
Measure the resistance of the return circuit between the intake air heaterrelay connector and battery negative.
I s resistance less than 10 ohms?
Ye s>>
Go To 6
No>>
Repair the return circuit shorted to battery negative.
6.SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE
Measure the voltage between the signal circuit of the intake air heater relay and battery negative.
Is the voltage greater than 1 volts?
Ye s>>
Repair the signal circuit shorted to Battery negative.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 7
7.ECM
Reconnect the ECM harness connectors.
Disconnect the intake air heater relay signal wire and use a jumper to connect it to battery negative.
Turn the ignition on.
With the scan tool, read DTCs.
Did DTC P2608?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
No>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 876 of 5267

When Monitored:
When the ignition is on.
Set Condition:
When the signal from the #2 Intake Air Heater output does not match the signal from the #2 Intake Air Heater
feedback.
Possible Causes
LOOSE CONNECTION
INTAKEAIRHEATERRELAY
SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE
ECM
INTERMITTENT CONDITION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.RELAY CLICKING
Ignition on, engine not running.
With the scan tool, actuate the Intake Air Heater relay.
Can you hear the Relay clicking?
Ye s>>
Go To 2
No>>
Go To 3
2.LOOSE CONNECTION
While the relay is clicking , wiggle the wiring harness and connectors.
Does this interrupt the clicking?
Ye s>>
Repair the poor connection.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Go To 3
3.INTAKE AIR HEATER RELAY
Turn the ignition off.
Remove the Intake Air Heater Relay.
Check connectors - Clean/repair as necessary.
Measure the resistance between the signal and return posts of the intake air heater relay.
Is the resistance between 15 and 25 Ohms?
Ye s>>
Go To 4
No>>
Replace the Intake Air Heater relay.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 877 of 5267

4.SIGNAL CIRCUIT SHORTED TO BATTERY NEGATIVE
Disconnect the ECM harness connector(s).
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the signal circuit of the intake air heaterrelay and battery negative.
Is the resistance greater than 100 K ohms?
Ye s>>
Go To 5
No>>
Repair signal circuit shorted to battery negative.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
5.HARNESS SHORTED
Measure the resistance between intake air heater relay signal circuit andall other ECM circuits in the ECM con-
nectors.
Is the resistance greater than 100k ohms?
Ye s>>
Go To 6
No>>
Repair the shorted harness.
6.ECM
Reconnect the ECM harness connectors.
Turn the ignition on.
Disconnect the intake air heater relay signal wire.
Did DTC P0542 or 2608 set?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure). (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
No>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
Page 881 of 5267

*CHECKING THE ACCELERATOR PEDAL SENSOR CALIBRATION
Possible Causes
MIS-WIRED APPS
VOLTAGE NOT CHANGING DURING SWEEP
THROTTLE PEDAL NOT MOVING FREELY
APPS
Diagnostic Test
1.MIS-WIRED APPS
Turn the ignition off.
Remove the APPS cover.
Inspect both APPS connector and ECM for proper wiring.
Are both connectors wired correctly?
Ye s>>
Go To 2
No>>
Repair mis-wired APPS connector at APPS or ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
2.THROTTLE PEDAL NOT MOVING FREELY
Ignition on, engine not running.
Look for proper Throttle operation.
Does the Throttle Pedal move freely between the upper and lower stops?
Ye s>>
Replace the APPS.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
No>>
Repair as necessary.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)