P0642

P0642-LOW VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT

P0642 - Low Voltage At The #2 Sensor Supply Circuit:

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
- (K668) 5-Volt shorted to ground
- (K668) 5-Volt supply shorted to another circuit
- Fan DTC
- Intermittent condition
- ECM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

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.

Q: Did P0483 set?

YES: Replace the Fan clutch assembly. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 2

2. (K668) 5-VOLT SHORTED TO GROUND





Turn the ignition off.
Disconnect the ECM harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between the (K668) #2 5-volt supply (fan speed sensor power) circuit in the sensor harness connector and battery negative.

Q: Is the resistance greater than 100k Ohms?

YES: Go To 3
NO: Repair the #2 (K668) 5-volt supply shorted to ground. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

3. (K668) 5-VOLT SUPPLY SHORTED TO ANOTHER CIRCUIT





Measure the resistance between the sensor (K668) #2 5-volt supply (fan speed sensor power) circuit in the ECM harness connector to all other circuits in the ECM harness connectors

Q: Is the resistance greater than 100k Ohms?

YES: Go To 4
NO: Repair the 5-volt supply shorted to another circuit. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1

4. FAN DTC
Reconnect the ECM harness connectors.
Reconnect the disconnected Fan harness connector.
Turn the ignition on.
With the scan tool, read DTCs.

Q: Is DTC P0483 set?

YES: Repair the Fan DTC. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 5

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.

Q: Is the voltage between 4.5 and 5.5 volts?

YES: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure).
NO: Replace the ECM. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1