Page 707 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.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 6
6.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 P0542 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 708 of 5267
P0542-HIGH VOLTAGE ON THE #1 INTAKE AIR HEATER RELAY
For a complete wiring diagramRefer to Section 8W.
Page 709 of 5267

When Monitored:
When the ignition is on.
Set Condition:
When the signal from the #1 Intake Air Heater output does not match the signal from the #1 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.
NOTE: 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)
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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.SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS
Measure the resistance between the signal circuit of the intake air heaterrelay and all other circuits in the ECM
harness connector.
Is the resistance greater than 100 K ohms?
Ye s>>
Go To 6
No>>
Repair signal circuit shorted to other circuits.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
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 746 of 5267

When Monitored:
Whilethekeyison.
Set Condition:
The commanded signal to the fuel lift pump relay does not match the feedbacksignal from the fuel lift pump
relay.
Possible Causes
DAMAGED WIRING HARNESS
LIFT PUMP DRIVER CIRCUIT SHORTED TO GROUND
ECM
TIPM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.LIFT PUMP DRIVER CIRCUIT SHORTED TO GROUND
Turn the ignition on, engine off.
Disconnect the ECM and TIPM connectors.
NOTE: Check connectors - Clean/repair as necessary.
Using an ohmmeter, measure the resistance of the lift pump driver wire between the ECM connector and ground.
Is the resistance less than 10 Ohms?
Ye s>>
Fix or repair the wire harness.
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.ECM
Turn Ignition off.
Connect the ECM and TIPM connectors.
Turn the ignition on, engine off.
Using a back probing tool 6801, back probe the lift pump logic pin in from TIPM connector.
Toggle the lift pump actuator with the Electronic Service Tool.
Using a 12 volt test light connected to battery negative, check the lift pump circuit at the TIPM connector.
NOTE: The test light must illuminate brightly.
Compare the brightness to that of a direct connection to the battery.
Does the test light cycle on and off and illuminate brightly?
Ye s>>
Go To 3
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 757 of 5267
P0646-LOW VOLTAGE DETECTED AT THE A/C CLUTCH RELAY
For a complete wiring diagramRefer to Section 8W.
Page 760 of 5267
P0647-HIGH VOLTAGE DETECTED AT THE A/C CLUTCH RELAY
For a complete wiring diagramRefer to Section 8W.
Page 778 of 5267

When Monitored:
With the ignition on. Battery voltage greater than 10 volts. A/C Switch on.
Set Condition:
A shorted condition is detected in the A/C clutch relay control circuit. One Trip Fault. Three good trips to turn
off the MIL.
Possible Causes
(C3) A/C COMPRESSOR CLUTCH CONTROL CIRCUIT SHORTED TO GROUND
A/C COMPRESSOR CLUTCH
TIPM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING).
Diagnostic Test
1.A/C COMPRESSOR CLUTCH OPERATION
Ignition on, engine not running.
With a scan tool under the PCM Actuators, actuate the A/C Clutch.
Is the A/C Clutch actuating?
Ye s>>
Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)
No>>
Go To 2
2.A/C CLUTCH CONTROL OPERATION FROM THE PCM
Turn the ignition off.
Disconnect the C2 TIPM harness connector.
Ignition on, engine not running.
Using the scan tool under the PCM Actuators, actuate the A/C Clutch.
With a 12-volt test light connected to ground, probe the (C13) A/C
Clutch Control circuit in the C2 TIPM harness connector.
Does the test light illuminate brightly and flash on an off?
Ye s>>
Go To 3
No>>
Perform the Diagnostic Procedure for P0645-A/C CLUTCH
CONTROL CIRCUIT. (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)