WOMS
B code body Medium severity

B1808 Lamp Tail Output Circuit Short To Battery

The OBD2 code B1808 indicates a short circuit in the tail lamp output circuit, meaning that the circuit is receiving power directly from the battery instead of functioning normally, which can cause the tail lights to...

Definition

The OBD2 code B1808 indicates a short circuit in the tail lamp output circuit, meaning that the circuit is receiving power directly from the battery instead of functioning normally, which can cause the tail lights to malfunction

Common causes

  • Shorted wiring or connectors
  • Faulty tail lamp assembly
  • Corroded or damaged connectors
  • Malfunctioning body control module (BCM)
  • Incorrectly installed or damaged aftermarket lighting
  • Grounding issues
  • Faulty fuses or relays

Common misdiagnoses

  • Faulty tail light bulbs
  • Defective tail light assembly
  • Wiring harness issues
  • Bad ground connections
  • Malfunctioning body control module (BCM)
  • Incorrectly installed aftermarket lighting
  • Shorted wiring in the trunk or rear area
  • Corroded connectors or terminals

Troubleshooting steps

  1. 1. Visual Inspection

    Check Wiring and Connectors: Inspect the wiring harness and connectors associated with the tail lamp circuit for any signs of damage, fraying, or corrosion

  2. 2. Look for Shorts

    Check for any wires that may be pinched, chafed, or touching metal surfaces that could cause a short to battery

  3. 3. Check Tail Lamp Bulbs

    Inspect Bulbs: Remove the tail lamp bulbs and inspect them for any signs of damage or improper installation. Replace any faulty bulbs

  4. 4. Test Bulb Sockets

    Ensure that the bulb sockets are clean and free of corrosion

  5. 5. Test the Tail Lamp Circuit

    Use a Multimeter: With the vehicle's ignition on, use a multimeter to check for voltage at the tail lamp connector. Compare the readings to the specifications in the vehicle's service manual

  6. 6. Check Ground Connections

    Ensure that the ground connections for the tail lamp circuit are secure and free of corrosion

  7. 7. Inspect the Tail Lamp Relay and Fuses

    Check Fuses: Locate the fuse for the tail lamps in the fuse box and check if it is blown. Replace it if necessary

  8. 8. Test the Relay

    If applicable, test the tail lamp relay to ensure it is functioning correctly

  9. 9. Scan for Additional Codes

    Use a Diagnostic Scanner: Check for any additional trouble codes that may provide more context or indicate related issues

  10. 10. Check for Short Circuits

    Perform a Continuity Test: Disconnect the battery and perform a continuity test on the tail lamp circuit to check for shorts to ground or battery

  11. 11. Inspect for Aftermarket Modifications

    If there are any aftermarket modifications (like trailer wiring), inspect them for proper installation and potential shorts

  12. 12. Repair or Replace Components

    Repair Damaged Wiring: If any damaged wiring is found, repair or replace it as necessary

  13. 13. Replace Faulty Components

    If any components (like the relay or connectors) are found to be faulty, replace them

  14. 14. Clear Codes and Test Drive

    Clear the Codes: After making repairs, clear the trouble codes using a diagnostic scanner

  15. 15. Test Drive the Vehicle

    Take the vehicle for a test drive to ensure that the issue is resolved and that the code does not return

  16. 16. Consult a Professional

    If the issue persists after following these steps, it may be necessary to consult a professional mechanic for further diagnosis and repair. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the OBD-II code B1808