B1806 – Lamp Tail Output Circuit Failure

The ODBII code B1806 indicates a failure in the tail lamp output circuit, which may involve issues with the wiring, connectors, or the tail lamp assembly itself.

The severity of ODBII code B1806 is moderate.

Common Causes For: B1805 Lamp Turn Signal Rear Output Circuit Short To Ground

• Faulty tail lamp assembly
• Damaged wiring or connectors
• Short circuit in the tail lamp circuit
• Blown fuse
• Faulty body control module (BCM)
• Corroded terminals
• Poor ground connection

Common misdiagnosis for B1806 Lamp Tail Output Circuit Failure

• Faulty tail light bulbs
• Bad tail light sockets
• Wiring issues or shorts in the tail light circuit
• Faulty body control module (BCM)
• Incorrectly installed or damaged connectors
• Grounding issues
• Faulty fuse related to the tail light circuit
• Malfunctioning switch or relay for the tail lights

Common Troubleshooting Steps

The OBD-II code B1806 refers to a “Lamp Tail Output Circuit Failure,” which typically indicates an issue with the tail lamp circuit in the vehicle. This code can be associated with various problems, including wiring issues, bulb failures, or problems with the body control module (BCM). Here are some common troubleshooting steps to diagnose and resolve the issue:

• Check for Additional Codes: Use an OBD-II scanner to check for any additional trouble codes that may provide more context or indicate related issues.
• Inspect Tail Lamp Bulbs: Check the tail lamp bulbs for any signs of damage or burnout. Replace any faulty bulbs.
• Examine Wiring and Connectors: Inspect the wiring harness and connectors associated with the tail lamp circuit for any signs of damage, corrosion, or loose connections.
• Look for frayed wires, broken connectors, or any signs of wear.
• Test the Tail Lamp Circuit: Use a multimeter to test the voltage and ground at the tail lamp socket. Ensure that the circuit is receiving the correct voltage when the tail lights are activated.
• Check for continuity in the wiring from the BCM to the tail lamp.
• Check the Body Control Module (BCM): If the wiring and bulbs are in good condition, the issue may lie with the BCM. Check for any signs of damage or malfunction.
• If possible, perform a BCM reset or reprogramming, as this can sometimes resolve communication issues.
• Inspect Fuses: Check the fuses related to the tail lamp circuit. Replace any blown fuses and ensure that the fuse box is in good condition.
• Look for Ground Issues: Ensure that the ground connections for the tail lamp circuit are secure and free of corrosion. A poor ground can lead to circuit failures.
• Perform a Visual Inspection: Conduct a thorough visual inspection of the entire tail lamp assembly and surrounding areas for any signs of damage or interference.
• Consult Wiring Diagrams: Refer to the vehicle’s wiring diagrams to understand the tail lamp circuit better and identify any potential problem areas.
• Clear Codes and Test Drive: After performing repairs, clear the trouble codes using the OBD-II scanner and take the vehicle for a test drive to see if the code returns.1
• Seek Professional Help: If the issue persists after following these steps, it may be necessary to consult a professional mechanic or technician for further diagnosis and repair. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the B1806 code.