P0643

P0643-SENSOR REFERENCE VOLTAGE 1 CIRCUIT HIGH





For complete wiring diagrams 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.

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 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. 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. Powertrain Verification Test

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition