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 761 of 5267

When Monitored:
When the ignition is on.
Set Condition:
When the signal from the A/C Clutch output does not match the signal from theA/C Clutch feedback.
Possible Causes
WIRING HARNESS OR CONNECTIONS
A/C CLUTCH CIRCUIT SHORTED TO EXTERNAL VOLTAGE
TIPM
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.A/C CLUTCH CIRCUIT SHORTED TO EXTERNAL VOLTAGE
Ignition off.
Disconnect the ECM and TIPM connectors.
NOTE: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
Using a Voltmeter, measure the voltage of the A/C Clutch Control Circuit between the TIPM connector and battery
negative..
Is the voltage less than 1 volt?
Ye s>>
Go To 2
Ye s>>
Repair or Replace the wiring harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
2.ECM
Ignition off.
Connect the ECM and TIPM connectors.
Ignition on, engine not running.
Using a back probing tool 6801, back probe the A/C clutch control circuit inthe TIPM connector.
Using a 12 volt test light connected to battery positive, check the transmission control circuit at the TIPM connector
while actuating the A/C clutch circuit with the Electronic Service Tool.
NOTE: The test light must illuminate brightly.
Compare the brightness to that of a direct connection to the battery.
Does the test light 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 763 of 5267
P0652-LOW VOLTAGE AT THE #1 SENSOR SUPPLY CIRCUIT
For a complete wiring diagramRefer to Section 8W.
Page 767 of 5267
P0653-HIGH VOLTAGE AT THE #1 SENSOR SUPPLY CIRCUIT
For a complete wiring diagramRefer to Section 8W.
Page 771 of 5267

For a complete wiring diagramRefer to Section 8W.
When Monitored:
With engine running.
Set Condition:
Low voltage detected at the APPS supply circuit or low voltage detected at the APPS 1 5–volt supply.
Possible Causes
(F855) APPS 5-VOLT SUPPLY OPEN
APPS HIGH RESISTANCE
(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO (K922) RETURN CIRCUIT
(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO BATTERY NEGATIVE
ECM
INTERMITTENT CONDITION
(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO OTHER CIRCUITS
APPS
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
1.(F855) 5-VOLT SUPPLY CIRCUIT SHORTED TO BATTERY NEGATIVE
Turn the ignition off.
Disconnect the ECM harness connectors.
Disconnect the APPS harness connector.
Check connectors - Clean/repair as necessary.
Measure the resistance of the APPS1 (F855) 5-volt supply circuit
between the sensor harness connector and battery negative
Is the resistance greater than 100 k ohms?
Ye s>>
Go To 2
No>>
Repair the (F855) 5-volt supply circuit shorted to battery
negative.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 775 of 5267

For a complete wiring diagramRefer to Section 8W.
When Monitored:
Whileengineisrunning.
Set Condition:
High voltage detected at the APPS supply circuit.
Possible Causes
(F855) 5-VOLT SUPPLY OPEN
(F855) 5-VOLT SUPPLY SHORT TO VOLTAGE
ECM
INTERMITTENT CONDITION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
1.(F855) 5-VOLT SUPPLY OPEN
Turn the ignition off.
Disconnect the APPS harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
Measure the voltage between the (F855) APPS #1 5-volt supply circuit
at the sensor connector and battery negative.
Is the voltage between 4.5 and 5.5 volts?
Ye s>>
Replace the APPS.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
No>>
Go To 2
2.(F855) 5-VOLT SUPPLY SHORT TO VOLTAGE
Turn the ignition off.
Disconnect the ECM harness connector(s).
NOTE: Check connectors - Clean/repair as necessary.
Ignition on, engine not running.
Measure the voltage between the (F855) APPS #1 5-volt supply circuit
in the sensor harness connector and battery negative.
Is the voltage less than 1 volt?
Ye s>>
Go To 3
No>>
Repair or replace the wiring harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 777 of 5267
P1272-A/C CLUTCH CONTROL CIRCUIT 2 LOW
For a complete wiring diagramRefer to Section 8W.