Page 753 of 5267
5.ECM
Turn the ignition off.
Disconnect the Fan harness connector.
Turn the ignition on.
Measure the voltage between the sensor (K668) #2 5-volt supply (fan
speed sensor power) circuit at the fan clutch harness connector and the
fan speed sensor ground.
Is the voltage between 4.5 and 5.5 volts?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diag-
nostic Procedure). (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)
No>>
Replace the ECM.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 754 of 5267
P0643-HIGH VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT
For a complete wiring diagramRefer to Section 8W.
Page 755 of 5267

When Monitored:
With the key on.
Set Condition:
Voltage detected on the #2 sensor supply circuit was above a calibrated value.
Possible Causes
FAN CLUTCH ASSEMBLY
(K668) 5-VOLT SHORTED TO VOLTAGE
INTERMITTENT CONDITION
ECM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.FAN CLUTCH ASSEMBLY
Disconnect the Fan clutch harness connector.
NOTE: Check connectors - Clean/repair as necessary.
With the scan tool, read DTCs.
Did P0483 set?
Ye s>>
Replace the Fan clutch assembly.
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.(K668) 5-VOLT SHORTED TO VOLTAGE
Disconnect the ECM harness connectors.
Disconnect the Fan harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Measure the voltage between the fan speed sensor (K668) 5-volt supply
circuit and battery negative.
Is the voltage greater than 1 volt?
Ye s>>
Repair the (K668) 5-volt supply shorted to voltage.
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 3
Page 763 of 5267
P0652-LOW VOLTAGE AT THE #1 SENSOR SUPPLY CIRCUIT
For a complete wiring diagramRefer to Section 8W.
Page 764 of 5267

When Monitored:
With the key on.
Set Condition:
Voltage detected on the sensor supply is below a calibrated value.
Possible Causes
ECM
(F855) #1 5-VOLT SUPPLY SHORTED TO GROUND
(F855) #1 5-VOLT SUPPLY SHORTED
FUEL RAIL PRESSURE
A/C PRESSURE SENSOR
MAP SENSOR
CAMSHAFT POSITION SENSOR
INTERMITTENT CONDITION
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE -
DIAGNOSIS AND TESTING)
Diagnostic Test
1.ECM
Turn the ignition off.
Disconnect the ECM 60 pin harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Turn the ignition on.
Measure the voltage between the Sensor (F855) #1 5-volt Supply and
the Sensor (K916) #1 Return pin at the ECM.
Is the voltage between 4.5 and 5.5 volts?
Ye s>>
Go To 2
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 765 of 5267

2.(F855) #1 5-VOLT SUPPLY SHORTED TO GROUND
Disconnect the Pressure sensors harness connectors and the engine
position sensor.
Measure the resistance between the (F855) #1 sensor supply circuits at
the ECM harness connector and battery negative.
Is the resistance greater than 100K Ohms?
Ye s>>
Go To 3
No>>
Repair the harness.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
3.FUEL RAIL PRESSURE
Reconnect the ECM harness connector.
While monitoring with the scan tool, disconnect the fuel rail pressure sensor.
Is DTC P0652 set?
Ye s>>
Go To 4
No>>
Replace the Fuel rail pressure sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
4.A/C PRESSURE SENSOR
While monitoring with the scan tool, disconnect the A/C pressure sensor.
Is DTC P0652 set?
Ye s>>
Go To 5
No>>
Replace the A/C pressure sensor.
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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5.MAP SENSOR
While monitoring with the scan tool, disconnect the map sensor.
Is DTC P0652 set?
Ye s>>
Go To 6
No>>
Replace the MAP sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
6.CAMSHAFT POSITION SENSOR
While monitoring with the scan tool, disconnect the Camshaft position sensor.
Is DTC P0652 set?
Ye s>>
Go To 7
No>>
Replace the Camshaft position sensor.
Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). (Refer to 8 - ELECTRICAL/ELEC-
TRONIC CONTROL MODULES/ENGINE CONTROL MODULE - DIAGNOSIS AND TESTING)
7.(F855) #1 5-VOLT SUPPLY SHORTED
Measure the resistance between the (F855) #1 sensor supply circuit of
the ECM harness connector and all other circuits in both ECM harness
connectors.
Is the resistance greater than 100K Ohms?
Ye s>>
Refer to the INTERMITTENT CONDITION Symptom (Diag-
nostic Procedure). (Refer to 9 - ENGINE - DIAGNOSIS
AND TESTING)
No>>
Repair the shorted circuit.
Perform POWERTRAIN VERIFICATION TEST VER - 1
(DIESEL). (Refer to 8 - ELECTRICAL/ELECTRONIC CON-
TROL MODULES/ENGINE CONTROL MODULE - DIAG-
NOSIS AND TESTING)
Page 767 of 5267
P0653-HIGH VOLTAGE AT THE #1 SENSOR SUPPLY CIRCUIT
For a complete wiring diagramRefer to Section 8W.