WOMS
B code body Medium severity

B1803 Lamp Turn Signal Rear Output Circuit Open

The OBD2 code B1803 indicates that there is an open circuit in the rear turn signal lamp output, meaning the vehicle's system is not detecting a proper connection or signal from the rear turn signal lamp

Definition

The OBD2 code B1803 indicates that there is an open circuit in the rear turn signal lamp output, meaning the vehicle's system is not detecting a proper connection or signal from the rear turn signal lamp

Common causes

  • Open circuit in the wiring
  • Faulty turn signal bulb
  • Defective turn signal relay
  • Poor ground connection
  • Damaged connector or terminals
  • Faulty body control module (BCM)

Common misdiagnoses

  • Faulty turn signal bulb
  • Bad turn signal switch
  • Damaged wiring or connectors
  • Faulty body control module (BCM)
  • Incorrectly installed or loose bulb socket
  • Grounding issues
  • Faulty relay
  • Corroded terminals

Troubleshooting steps

  1. 1. Check the Vehicle's Manual

    Refer to the vehicle's service manual for specific information about the turn signal circuit and wiring diagrams

  2. 2. Visual Inspection

  3. 3. Inspect the rear turn signal bulbs for any signs of damage or burnout. Replace any faulty bulbs

  4. 4. Check the bulb sockets for corrosion or damage

  5. 5. Look for any damaged or frayed wiring in the turn signal circuit, especially around the rear lights

  6. 6. Test the Bulb

  7. 7. Remove the bulb and test it with a multimeter to ensure it is functioning properly

  8. 8. If the bulb is good, reinstall it and ensure it is seated correctly in the socket

  9. 9. Check the Fuses

  10. 10. Locate the fuse box and check for any blown fuses related to the turn signal circuit. Replace any blown fuses

  11. 11. Inspect the Wiring Harness

  12. 12. Follow the wiring harness from the rear turn signal to the main harness. Look for any signs of wear, damage, or disconnection

  13. 13. Ensure all connectors are secure and free of corrosion

  14. 14. Test the Turn Signal Switch

  15. 15. The turn signal switch on the steering column can sometimes fail. Test the switch for continuity using a multimeter

  16. 16. If the switch is faulty, it may need to be replaced

  17. 17. Check for Ground Issues

  18. 18. Ensure that the ground connection for the rear turn signal is secure and free of corrosion. A poor ground can cause an open circuit

  19. 19. Scan for Additional Codes

  20. 20. Use an OBD-II scanner to check for any additional trouble codes that may provide more context to the issue

  21. 21. Perform a Continuity Test

  22. 22. Use a multimeter to perform a continuity test on the wiring from the turn signal bulb socket back to the turn signal relay or module. This will help identify any breaks in the circuit

  23. 23. Inspect the Turn Signal Relay/Module

  24. 24. If all else checks out, the turn signal relay or module may be faulty. Test or replace it as necessary. 1

  25. 25. Clear the Code

  26. 26. After performing repairs, clear the trouble code using an OBD-II scanner and take the vehicle for a test drive to see if the code returns. If you are not comfortable performing these steps or if the issue persists after troubleshooting, it may be best to consult a professional mechanic for further diagnosis and repair