B1808 – Lamp Tail Output Circuit Short To Battery

The ODBII 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.

The severity of ODBII code B1808 is moderate.

Common Causes For: B1807 Lamp Tail Output Circuit Open

• 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 misdiagnosis for B1808 Lamp Tail Output Circuit Short To Battery

• 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

Common Troubleshooting Steps

The OBD-II code B1808 indicates a problem with the tail lamp output circuit, specifically a short to battery. This code is often related to issues in the vehicle’s lighting system, particularly the tail lights. Here are some common troubleshooting steps to diagnose and resolve the issue:

• 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.
• **Look for Shorts: Check for any wires that may be pinched, chafed, or touching metal surfaces that could cause a short to battery.
• 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.
• **Test Bulb Sockets: Ensure that the bulb sockets are clean and free of corrosion.
• 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.
• **Check Ground Connections: Ensure that the ground connections for the tail lamp circuit are secure and free of corrosion.
• 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.
• **Test the Relay: If applicable, test the tail lamp relay to ensure it is functioning correctly.
• Scan for Additional Codes: **Use a Diagnostic Scanner: Check for any additional trouble codes that may provide more context or indicate related issues.
• 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.
• **Inspect for Aftermarket Modifications: If there are any aftermarket modifications (like trailer wiring), inspect them for proper installation and potential shorts.
• Repair or Replace Components: **Repair Damaged Wiring: If any damaged wiring is found, repair or replace it as necessary.
• **Replace Faulty Components: If any components (like the relay or connectors) are found to be faulty, replace them.
• Clear Codes and Test Drive: **Clear the Codes: After making repairs, clear the trouble codes using a diagnostic scanner.
• **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.
• 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.