P0642

P0642-SENSOR REFERENCE VOLTAGE 1 CIRCUIT LOW





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.

Theory of Operation

This sensor supply circuit provides a 5-volt supply to the Crankshaft Position Sensor. A MIL lamp will be lit immediately after this diagnostic runs and fails. The MIL lamp will turn off once the diagnostic runs and passes in 4 consecutive drive cycles.

- When Monitored:
With the key on.

- Set Condition:
Voltage detected on the 5-volt sensor supply circuit is below a calibrated value.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure

1. ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, record all Freeze frame data.
3. With the scan tool, erase DTCs.
4. Turn the ignition off for 30 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC reset?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION - DIESEL (Diagnostic Procedure). Intermittent Condition Test

2. CRANKSHAFT POSITION SENSOR
1. Ignition on.
2. Disconnect the Crankshaft Position Sensor.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the voltage on the (K824) 5-volt Supply circuit at the Crankshaft Position Sensor harness connector.

Is the voltage reading between 4.9 and 5.1 volts?

Yes

- Replace the Crankshaft Position Sensor.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Go To 3

3. (K824) 5-VOLT SHORTED TO GROUND




1. Turn the ignition off.
2. Disconnect the ECM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the resistance between ground and the (K824) 5-volt Supply circuit at the Crankshaft Position Sensor sensor harness connector.

Is the resistance below 10k ohms?

Yes

- Repair the short to ground in the (K824) 5-volt Supply circuit.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Go To 4

4. (K824) 5-VOLT SHORTED
1. Measure the resistance between the (K824) 5-volt Supply circuit and all other circuits in the ECM C1 connector.

Is the resistance below 10k ohms between the (K854) 5-volt Supply circuit and any of the circuits?

Yes

- Repair the short to the circuit that measured less than 10k ohms.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test

No

- Replace the ECM.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test