P0642

P0642-SENSOR REFERENCE VOLTAGE 1 CIRCUIT LOW





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 is below a calibrated value.







Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test


1. CRANKSHAFT POSITION SENSOR

Turn the ignition on.

While monitoring with the scan tool, disconnect the Crankshaft speed sensor.


NOTE: Check connectors - Clean/repair as necessary.

With the scan tool, read DTCs.

Did P0483 set?

Yes

- Replace Crankshaft speed sensor.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 2

2. (K824) 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 (K824) #2 5-volt supply circuit in the sensor harness connector and battery negative.

Is the resistance greater than 100k Ohms?

Yes

- Go To 3

No

- Repair the #2 (K824) 5-volt supply shorted to ground.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

3. (K824) 5-VOLT SUPPLY SHORTED TO ANOTHER CIRCUIT

Measure the resistance between the sensor (K824) #2 5-volt supply 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. Powertrain Verification Test

4. CRANKCASE POSITION SENSOR DTC

Reconnect the ECM harness connectors.

Reconnect the disconnected Crankcase position sensor harness connector.

Turn the ignition on.

With the scan tool, read DTCs.

Is DTC P0483 set?

Yes

- Repair the Crankcase position sensor DTC.
- Perform POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 5

5. ECM

Turn the ignition off.

Disconnect the Crankcase position sensor harness connector.

Turn the ignition on.

Measure the voltage between the sensor (K824) #2 5-volt supply circuit at the Crankcase position sensor harness connector and the Crankcase position sensor ground.

Is the voltage between 4.5 and 5.5 volts?

Yes

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Intermittent Condition

No

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