P0642 LOW VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT
When Monitored and Set Condition:
When Monitored: With the key on.
Set Condition: Voltage detected on the #2 sensor supply circuit is below a calibrated value.
- POSSIBLE CAUSES
- FAN CLUTCH ASSEMBLY
- (F856) 5-VOLT SHORTED TO GROUND
- (F856) 5-VOLT SUPPLY SHORTED TO ANOTHER CIRCUIT
- FAN DTC
- INTERMITTENT CONDITION
- ECM
DIAGNOSTIC PROCEDURE
-
Disconnect the Fan clutch harness connector.
NOTE: Check connectors - Clean/repair as necessary.
With the DRBIII®, read DTCs. Did P0483 set?
Yes --> Replace the Fan clutch assembly. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
No --> Go To 2 -
Turn the ignition off. Disconnect the ECM harness connector.
NOTE: Check connectors - Clean/repair as necessary.
Measure the resistance between the (F856) #2 5-volt supply (fan speed sensor power) circuit in the sensor harness connector and battery negative. Is the resistance greater than 100k Ohms?
Yes --> Go To 3
No --> Repair the #2 (F856) 5-volt supply shorted to ground. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). -
Measure the resistance between the sensor (F856) #2 5-volt supply (fan speed sensor power) circuit in the ECM harness connector to all other circuits in the ECM harness connectors Is the resistance greater than 100k Ohms?
Yes --> Go To 4
No --> Repair the 5-volt supply shorted to another circuit. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). -
Reconnect the ECM harness connectors. Reconnect the disconnected Fan harness connector. Turn the ignition on. With the DRBIII®, read DTCs. Is DTC P0483 set?
Yes --> Repair the Fan DTC. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
No --> Go To 5 -
Turn the ignition off. Disconnect the Fan harness connector. Turn the ignition on. Measure the voltage between the sensor (F856) #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?
Yes --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
No --> Replace the ECM. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).