P0642-SENSOR REFERENCE VOLTAGE 1 CIRCUIT LOW
For a complete wiring diagram Refer to Section 8W
- When Monitored:
With the ignition on.
- Set Condition:
The ECM detects a low voltage on the Sensor Supply 1 circuit for 0.16 second
| Possible Causes |
| INTERMITTENT DTC |
| 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND |
| CAMSHAFT POSITION SENSOR |
| ACCELERATOR PEDAL POSITION SENSOR |
| ENGINE CONTROL MODULE |
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 1 provides 5 volts to the Camshaft Position Sensor and the Accelerator Pedal Position Sensor No. 1.
Diagnostic Test
1. CHECK FOR ACTIVE DTCTurn 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, View DTCs.
Is the status Active for this DTC?
Yes
- Go To2
No
- Refer to the *CHECKING FOR AN INTERMITTENT DTC Diagnostic Procedure. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
2. CAMSHAFT POSITION SENSOR
Turn the ignition off.
Disconnect the Camshaft Position Sensor harness connector.
Turn the ignition on.
Measure the voltage of the (K844) Camshaft Position Sensor 5 Volt Supply circuit.
Is the voltage above 4.6 volts?
Yes
- Replace the Camshaft Position Sensor.
- Perform the ECM VERIFICATION TEST. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
No
- Go To3
3. ACCELERATOR PEDAL POSITION SENSOR NO. 1
Turn the ignition off.
Disconnect the Accelerator Pedal Position Sensor harness connector.
Turn the ignition on.
Measure the voltage of the (K852) Accelerator Pedal Position Sensor No. 1 5 Volt Supply circuit.
Is the voltage above 4.6 volts?
Yes
- Replace the Accelerator Pedal Position Sensor.
- Perform the ECM VERIFICATION TEST. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
No
- Go To4
4. 5-VOLT SUPPLY CIRCUIT SHORTED TO GROUND
Turn the ignition off.
Disconnect the ECM harness connectors.
Measure the resistance between ground and the (K844) Camshaft Position Sensor 5 Volt Supply circuit.
Measure the resistance between ground and the (K852) Accelerator Pedal Position Sensor No. 1 5 Volt Supply circuit.
Is the resistance above 1000 ohms for each circuit?
Yes
- Go To5
No
- Repair the 5-Volt Supply circuit that measures below 1000 ohms for a short to ground.
- Perform the ECM VERIFICATION TEST. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING)
5. ENGINE CONTROL MODULE (ECM)
Turn the ignition off.
Inspect the (K844) Camshaft Position Sensor 5 Volt Supply circuit between the Camshaft Position Sensor and the ECM.
Inspect the (K852) Accelerator Pedal Position Sensor No. 1 5 Volt Supply circuit between the Accelerator Pedal 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)
No
- 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)