WOMS
P code powertrain Medium severity

P1804 Transmission 4-Wheel Drive High Indicator Circuit Failure

The OBD2 code P1804 indicates a malfunction in the transmission's 4-wheel drive high indicator circuit, which means the system is unable to properly signal or detect the status of the 4WD high mode

Definition

The OBD2 code P1804 indicates a malfunction in the transmission's 4-wheel drive high indicator circuit, which means the system is unable to properly signal or detect the status of the 4WD high mode

Common causes

  • Faulty 4WD high indicator light
  • Damaged wiring or connectors in the circuit
  • Malfunctioning transfer case control module
  • Defective 4WD switch
  • Poor ground connection
  • Short circuit in the wiring harness
  • Corroded connectors or terminals
  • Faulty transmission control module (TCM)

Common misdiagnoses

  • Faulty transfer case
  • Bad transmission control module (TCM)
  • Defective 4WD switch
  • Wiring issues or shorts in the circuit
  • Malfunctioning dashboard indicator light
  • Incorrectly diagnosed transmission problems
  • Faulty vehicle speed sensor
  • Issues with the body control module (BCM)

Troubleshooting steps

  1. 1. Check the Vehicle's Owner Manual

    Refer to the owner's manual for specific information regarding the 4WD system and any related components

  2. 2. Visual Inspection

    Inspect the wiring and connectors associated with the 4WD system, particularly those leading to the transfer case and the indicator light

  3. 3. Look for any signs of damage, corrosion, or loose connections

  4. 4. Check the 4WD Indicator Light

    Ensure that the 4WD indicator light on the dashboard is functioning correctly. If the light is burned out, it may not indicate the proper status

  5. 5. Scan for Additional Codes

    Use an OBD-II scanner to check for any additional trouble codes that may provide more context or indicate related issues

  6. 6. Test the Transfer Case Shift Motor

    The transfer case shift motor is responsible for engaging and disengaging the 4WD system. Test the motor for proper operation

  7. 7. Check for any binding or mechanical issues in the transfer case

  8. 8. Inspect the 4WD Control Module

    If equipped, check the 4WD control module for faults. This may involve checking for proper power and ground to the module

  9. 9. Check for Short Circuits or Open Circuits

    Use a multimeter to test the continuity of the wiring in the 4WD indicator circuit. Look for any shorts to ground or open circuits

  10. 10. Test the 4WD Switch

    If the vehicle has a manual switch for engaging 4WD, test the switch for proper operation. Ensure it is functioning as intended

  11. 11. Check for Fluid Levels

    Ensure that the transfer case has the proper fluid level and that the fluid is in good condition. Low or contaminated fluid can affect operation

  12. 12. Clear Codes and Test Drive

    After performing any repairs or adjustments, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.1

  13. 13. Consult a Professional

    If the issue persists after performing these steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific make and model of your vehicle.Conclusion Troubleshooting OBD-II code P1804 involves a systematic approach to identify and resolve issues within the 4WD system. Always ensure safety precautions are taken when working on a vehicle, and consult professional help if needed