WOMS
P code powertrain Medium severity

P1868 Transmission Automatic 4-Wheel Drive Indicator (Lamp) Circuit Failure

The OBD2 code P1868 indicates a failure in the circuit responsible for the 4-wheel drive indicator lamp in an automatic transmission system

Definition

The OBD2 code P1868 indicates a failure in the circuit responsible for the 4-wheel drive indicator lamp in an automatic transmission system

Common causes

  • Faulty 4WD indicator lamp
  • Damaged wiring or connectors
  • Failed transmission control module (TCM)
  • Malfunctioning transfer case control module
  • Short circuit in the circuit
  • Open circuit in the circuit
  • Corroded connectors
  • Faulty transmission range sensor
  • Issues with the vehicle's body control module (BCM)

Common misdiagnoses

  • Faulty transmission control module (TCM)
  • Defective vehicle speed sensor (VSS)
  • Malfunctioning transfer case control module
  • Wiring issues or shorts in the circuit
  • Bad ground connections
  • Faulty 4WD switch
  • Incorrectly diagnosed transmission issues
  • Battery or charging system problems
  • Faulty dashboard indicator light
  • Software issues or updates needed in the vehicle's computer system

Troubleshooting steps

  1. 1. Check the Vehicle's Manual

    Refer to the vehicle's service manual for specific information related to the 4WD system and the indicator circuit. This can provide insights into the wiring diagrams and component locations

  2. 2. Visual Inspection

    Wiring and Connectors: Inspect the wiring harness and connectors related to the 4WD indicator circuit for any signs of damage, corrosion, or loose connections

  3. 3. Fuses

    Check the fuses associated with the 4WD system to ensure they are intact

  4. 4. Scan for Additional Codes

    Use an OBD-II scanner to check for any additional trouble codes that may be present. Other codes can provide context and help identify related issues

  5. 5. Test the 4WD Indicator Lamp

    Functionality: Verify that the 4WD indicator lamp itself is functioning correctly. You can do this by applying power directly to the lamp to see if it lights up

  6. 6. Bulb Replacement

    If the bulb is burnt out, replace it and clear the code to see if it returns

  7. 7. Check the 4WD Switch

    Test the 4WD switch (if applicable) for proper operation. Ensure that it is making good contact and that it is functioning as intended

  8. 8. Inspect the Transfer Case Control Module (TCCM)

    If your vehicle is equipped with a TCCM, check for proper operation. This module controls the 4WD system and may need to be tested or reprogrammed

  9. 9. Test for Ground and Power

    Use a multimeter to check for proper voltage and ground at the 4WD indicator circuit. Ensure that the circuit is receiving the correct voltage when the 4WD system is engaged

  10. 10. Check for Short Circuits

    Inspect the circuit for any short circuits to ground or power. This can cause the indicator to malfunction

  11. 11. Perform a System Reset

    Clear the trouble code using an OBD-II scanner and see if it returns after a test drive. Sometimes, a reset can resolve temporary glitches

  12. 12. Consult Technical Service Bulletins (TSBs)

    Look for any TSBs related to the 4WD system for your specific vehicle make and model. Manufacturers may have issued updates or fixes for known issues.1

  13. 13. Professional Diagnosis

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or dealership. They may have specialized tools and knowledge to diagnose more complex issues.Conclusion By following these troubleshooting steps, you can systematically identify and address the cause of the P1868 code. Always ensure safety precautions are taken when working on vehicle electrical systems