P0643

P0643-SENSOR REFERENCE VOLTAGE 1 CIRCUIT HIGH





For a complete wiring diagram Refer to Diagrams/Electrical.

Theory of Operation


This sensor supply circuit provides a 5-volt supply to the engine speed 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 #2 sensor supply circuit was above a calibrated value.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Initial Inspection and Diagnostic Overview


Diagnostic Test


1. (K824) 5-VOLT SHORTED TO VOLTAGE
Disconnect the ECM harness connectors.

NOTE: Check connectors - Clean/repair as necessary.

Measure the resistance between the #2 sensor supply circuit and all other circuits in the ECM connectors.
Is the resistance less than 10 ohms?

Yes


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


No


- Go To 2



2. (K824) 5-VOLT SHORTED TO VOLTAGE
Disconnect the ECM harness connectors.
Disconnect the Crankcase position sensor harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Measure the voltage between the Crankcase position sensor (K824) 5-volt supply circuit and battery negative.
Is the voltage greater than 1 volt?

Yes


- Repair the (K824) 5-volt supply shorted to voltage.
- Perform POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test


No


- Go To 3



3. ECM
Turn the ignition off.
Reconnect the ECM harness connectors.
Turn the ignition on.
Measure the voltage between the (K824) 5-volt supply circuit in the sensor harness connector and battery negative.
Is the voltage greater than 6 volts?

Yes


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


No


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