P0643-SENSOR REFERENCE VOLTAGE 1 TOO HIGH

For a complete wiring diagram Refer to Section 8W

When Monitored:
With the ignition on.
Set Condition:
The ECM detects a short to voltage on the Sensor Supply 1 circuit for 0.16 second.

(K852) ACCELERATOR PEDAL POSITION NO. 1 5 VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE

(K844) CAMSHAFT POSITION SENSOR 5 VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

Theory of Operation

The ECM contains 3 internal 5–Volt Sensor Supply sources. Each 5–Volt Supply source is split into parallel circuits to provide 5 volts to multiple sensors. Sensor Supply 2 provides 5 volts to the Accelerator Pedal Position Sensor No. 1 and the Camshaft Position Sensor.

Diagnostic Test

1. CHECK FOR ACTIVE DTC

Turn the ignition on.
With the scan tool, erase ECM DTCs.
Turn the ignition off for 10 seconds.
Turn the ignition on.
With the scan tool, select View DTCs.

Is the status Active for this DTC?

Yes

Go To 2

Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

2. (K852) ACCELERATOR PEDAL POSITION SENSOR NO. 1 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.
Disconnect the Accelerator Pedal Position Sensor harness connector.
Disconnect the ECM harness connectors.
Remove the Main Relay.
Connect a jumper wire between cavity B7 and cavity B9 of the Main Relay connector.
Turn the ignition on.
Measure the voltage on the (K852) Accelerator Pedal Position Sensor No. 1 5-Volt Supply circuit.

Is the voltage below 1.0 volt?

Yes

Go To 3

Repair the (K852) Accelerator Pedal Position Sensor No. 1 5 Volt Supply circuit for a short to voltage.
Perform the ECM VERIFICATION TEST. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

3. (K844) CAMSHAFT POSITION SENSOR 5-VOLT SUPPLY CIRCUIT SHORTED TO VOLTAGE

Turn the ignition off.
Disconnect the Camshaft Position Sensor harness connector.
Turn the ignition on.
Measure the voltage on the (K844) Camshaft Position Sensor 5 Volt Supply circuit.

Is the voltage below 1.0 volt?

Yes

Go To 4

Repair the (K844) Camshaft Position Sensor 5 Volt Supply circuit for a short to voltage.
Perform the ECM VERIFICATION TEST. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

4. ENGINE CONTROL MODULE (ECM)

Turn the ignition off.
Inspect the (K852) Accelerator Pedal Position Sensor No. 1 5 Volt Supply circuit between the Accelerator Pedal Position Sensor and the ECM.
Inspect the (K844) Camshaft Position Sensor 5 Volt Supply circuit between the Camshaft Position Sensor and the ECM.
Look for any chafed, pierced, pinched, or partially broken wires.
Look for broken, bent, pushed out or corroded terminals.
Refer to any Technical Service Bulletins that may apply.

Were any problems found?

Yes

Repair as necessary.

Perform the ECM VERIFICATION TEST. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)

Replace and program the Engine Control Module in accordance with the Service Information.
Perform the ECM VERIFICATION TEST. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)