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  • P0643 High Voltage At The #2 Sensor Supply Circuit

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    P0643 HIGH VOLTAGE AT THE #2 SENSOR SUPPLY CIRCUIT

    When Monitored and Set Condition:

    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
    • (F856) 5-VOLT SHORTED TO VOLTAGE
    • INTERMITTENT CONDITION
    • ECM

    DIAGNOSTIC PROCEDURE

    1. Disconnect the Fan clutch harness connector. With the DRBIII®, read DTCs. Did P0483 set?
      Yes --> Replace the Fan clutch assembly. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 2
    2. 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 (F856) 5-volt supply circuit and battery negative. Is the voltage greater than 1 volt?
      Yes --> Repair the (F856) 5-volt supply shorted to voltage. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Go To 3
    3. Turn the ignition off. Reconnect the ECM harness connectors. Turn the ignition on. Measure the voltage between the (F856) 5-volt supply circuit in the sensor harness connector and battery negative. Is the voltage greater than 6 volts?
      Yes --> Replace the ECM. Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).
      No --> Refer to the SYMPTOM: INTERMITTENT CONDITION Symptom (Diagnostic Procedure). Perform POWERTRAIN VERIFICATION TEST VER - 1 (DIESEL).

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