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  • P0838 4WD Mode Sensor Low

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    Mopar1973Man

    P0838 4WD MODE SENSOR LOW

    When Monitored and Set Condition:

    When Monitored: Continuously with the ignition key on.
    Set Condition: When the 4WD Mode Sensor input circuit voltage falls below 0.3 volts for 5.72 seconds.

    POSSIBLE CAUSES

    • TRANSFER CASE POSITION SENSOR INPUT CIRCUIT SHORT TO GROUND
    • TRANSFER CASE POSITION SENSOR INPUT CIRCUIT SHORT TO SENSOR RETURN CIRCUIT
    • TRANSFER CASE POSITION SENSOR
    • POWERTRAIN/ENGINE CONTROL MODULE
    • INTERMITTENT OPERATION

    DIAGNOSTIC PROCEDURE

    1. With the DRBIII(R), record and erase DTC's. Start the engine and cycle the Transfer Case through all positions. With the DRBIII(R), read Transfer Case DTCs. Is the Good Trip Counter equal to zero?
      Yes --> Go To 2
      No --> Go To 6
    2. Turn the ignition off to the lock position. Disconnect the Powertrain Control Module harness connector.
      CAUTION: IF EQUIPPED WITH NGC CONTROLLER, DO NOT PROBE THE PCM HARNESS CONNECTORS. PROBING THE PCM HARNESS CONNECTORS WELL DAMAGE THE PCM TERMINALS RESULTING IN POOR TERMINAL TO PIN CONNECTION. INSTALL MILLER SPECIAL TOOL #8815 TO PERFORM DIAGNOSIS.
      Disconnect the Transfer Case Position Sensor harness connector.
      NOTE: Check connectors - Clean/repair as necessary.
      Measure the resistance between ground and the Transfer Case Position Sensor Input circuit. Is the resistance below 5.0 ohms?
      Yes --> Repair the Transfer Case Position Sensor input circuit for a short to ground.
      No --> Go To 3
    3. Measure the resistance between the Transfer Case Position Sensor Input circuit and the Sensor Return circuit in the PCM/ECM harness connector. Is the resistance above 1000.0 ohms?
      Yes --> Go To 4
      No --> Repair the Transfer Case Position Sensor Input circuit for a short to the Sensor Return circuit.
    4. Measure the resistance between the Transfer Case Position Sensor Input circuit and the Sensor Return circuit in the PCM/ECM harness connector. Is the resistance between 55 ohms and 1.3k ohms?
      Yes --> Go To 5
      No --> Replace the Transfer Case Position Sensor.
    5. If there are no possible causes remaining, view repair. Repair Replace and program the Powertrain/Engine Control Module. Refer to ELECTRONIC CONTROL MODULES . Perform the appropriate Powertrain verification test.
    6. The conditions to set this DTC are not present at this time.
      NOTE: Use the Freeze Frame Data to help duplicate the conditions that set the DTC. Pay particular attention to the DTC set conditions, such as, VSS, MAP, ECT, and Load.
      NOTE: Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires.
      NOTE: Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals.
      NOTE: Refer to any technical service bulletins that may apply.
      Were there any problems found?
      Yes --> Repair as necessary.
      No --> Test Complete.


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