WOMS
P code powertrain Medium severity

P0804 1-4 Upshift (Skip Shift) Lamp Control Circuit Malfunction

The OBD2 code P0804 indicates a malfunction in the control circuit for the 1-4 upshift (skip shift) lamp, which is part of the vehicle's transmission system

Definition

The OBD2 code P0804 indicates a malfunction in the control circuit for the 1-4 upshift (skip shift) lamp, which is part of the vehicle's transmission system

Common causes

  • Faulty skip shift solenoid
  • Wiring issues (shorts, opens, or corrosion)
  • Poor connections or damaged connectors
  • Malfunctioning transmission control module (TCM)
  • Faulty vehicle speed sensor
  • Issues with the engine control module (ECM)
  • Incorrect transmission fluid level or condition
  • Mechanical transmission problems

Common misdiagnoses

  • Faulty transmission control module (TCM)
  • Malfunctioning shift solenoid
  • Wiring issues or shorts in the circuit
  • Defective skip shift solenoid
  • Incorrectly diagnosed transmission problems
  • Faulty vehicle speed sensor
  • Issues with the clutch or clutch actuator
  • Problems with the engine control module (ECM)

Troubleshooting steps

  1. 1. Check the Vehicle's Owner Manual

    Refer to the vehicle's service manual for specific information regarding the skip shift feature and the associated components

  2. 2. Visual Inspection

    Inspect the wiring and connectors associated with the skip shift system for any signs of damage, corrosion, or loose connections

  3. 3. Check the condition of the skip shift solenoid (if applicable) and its wiring

  4. 4. Scan for Additional Codes

    Use an OBD-II scanner to check for any other trouble codes that may be present. This can provide additional context for the issue

  5. 5. Test the Skip Shift Solenoid

    If the vehicle is equipped with a skip shift solenoid, test its operation. This may involve checking for proper voltage and ground at the solenoid connector

  6. 6. If the solenoid is not functioning correctly, it may need to be replaced

  7. 7. Inspect the Skip Shift Lamp

    Check the skip shift indicator lamp on the dashboard. Ensure that it is functioning properly and that the bulb is not burned out

  8. 8. Check the Transmission Control Module (TCM)

    Inspect the TCM for any faults. If the TCM is not sending the correct signals to the skip shift system, it may need to be reprogrammed or replaced

  9. 9. Test the Circuit

    Use a multimeter to test the continuity of the wiring in the skip shift circuit. Look for any breaks or shorts in the wiring

  10. 10. Check for proper voltage at the skip shift circuit when the vehicle is in the appropriate conditions for the skip shift feature to activate

  11. 11. Clear the Codes and Test Drive

    After performing the above checks and repairs, clear the trouble codes using the OBD-II scanner

  12. 12. Take the vehicle for a test drive to see if the code reappears

  13. 13. Consult a Professional

    If the issue persists after performing the above steps, it may be necessary to consult a professional mechanic or technician who has experience with the specific make and model of your vehicle.Additional Notes: - Always ensure that you are working safely and following proper procedures when diagnosing and repairing vehicle issues. - If you are not comfortable performing these steps, it is advisable to seek help from a qualified technician