P0643

P0643-HIGH VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT

P0643 - High Voltage At The #2 Sensor Supply Circuit:

WHEN MONITORED
With the key on.

SET CONDITION
Voltage detected on the #2 sensor supply circuit was above a calibrated value.

POSSIBLE CAUSES
- Fan clutch assembly
- (K668) 5-Volt shorted to voltage
- Intermittent condition
- ECM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding.

Diagnostic Test

1. FAN CLUTCH ASSEMBLY
Disconnect the Fan clutch harness connector.

NOTE: Check connectors - Clean/repair as necessary.

With the scan tool, read DTCs.

Q: Did P0483 set?

YES: Replace the Fan clutch assembly. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 2

2. (K668) 5-VOLT SHORTED TO VOLTAGE





Disconnect the ECM harness connectors.
Disconnect the Fan harness connector.

NOTE: Check connectors - Clean/repair as necessary.

Measure the voltage between the fan speed sensor (K668) 5-volt supply circuit and battery negative.

Q: Is the voltage greater than 1 volt?

YES: Repair the (K668) 5-volt supply shorted to voltage. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Go To 3

3. ECM





Turn the ignition off.
Reconnect the ECM harness connectors.
Turn the ignition on.
Measure the voltage between the (K668) 5-volt supply circuit in the sensor harness connector and battery negative.

Q: Is the voltage greater than 6 volts?

YES: Replace the ECM. Perform the POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL). Powertrain Verification Test - Ver 1
NO: Refer to the INTERMITTENT CONDITION Symptom (Diagnostic Procedure).