Engine Code
P0643-PRIMARY 5-VOLT SUPPLY CIRCUIT HIGHP0643-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.
POSSIBLE CAUSES
- (F855) Primary 5-volt supply shorted to battery voltage
- PCM
Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.
Diagnostic Test
1. ACTIVE DTC
Ignition on, engine not running.
With a scan tool, read DTCs.
Q: Is the DTC active at this time?
YES: Go To 2
NO: Refer to the INTERMITTENT CONDITION Diagnostic Procedure. Component Tests and General Diagnostics
Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
2. (F855) PRIMARY 5-VOLT SUPPLY SHORTED TO BATTERY VOLTAGE
Turn the ignition off.
Disconnect the C2 PCM harness connector.
Disconnect all the Sensors that share the (F855) Primary 5-volt Supply circuit.
NOTE: Improperly installed aftermarket accessories can cause this DTC to set. Check for wiring added by customer.
Ignition on, engine not running.
Measure the voltage on the (F855) Primary 5-volt Supply circuit at the CKP Sensor harness connector.
Q: Is the voltage above 5.2 volts?
YES: Repair the short to battery voltage in the (F855) Primary 5-volt Supply circuit. Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test
NO: Go To 3
3. PCM
NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.
Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.
Q: 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