P0643

P0643-PRIMARY 5-VOLT SUPPLY CIRCUIT HIGH







- When Monitored:
Ignition on.

- Set Condition:
When the PCM recognizes the Primary 5-volt Supply circuit voltage is too high. One Trip Fault. ETC light is flashing.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC

NOTE: Improperly installed aftermarket accessories can cause this DTC to set. Check for any improperly installed aftermarket accessories before continuing with this test.

1. Start the engine and allow it to idle for at least 60 seconds.

WARNING: When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing. Failure to follow these instructions may result in possible serious or fatal injury.

2. With a scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Refer to the INTERMITTENT CONDITION Diagnostic Procedure. . Intermittent Condition Test

2. (F855) PRIMARY 5-VOLT SUPPLY SHORTED TO VOLTAGE





NOTE: Improperly installed aftermarket accessories can cause this DTC to set. Check for wiring added by customer.

1. Turn the ignition off.
2. Disconnect the C2 PCM harness connector.
3. Disconnect all the Sensors that share the (F855) Primary 5-volt Supply circuit.
4. Ignition on, engine not running.
5. Measure the voltage on the (F855) Primary 5-volt Supply circuit at the CKP Sensor harness connector.

Is there any voltage present?

Yes

- Repair the short to voltage in the (F855) Primary 5-volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Go To 3

3. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the related Sensors and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched, or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the related Sensor and Control Module connectors.
4. Search for any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test

No

- Replace and program the Powertrain Control Module.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test