B1805 – Lamp Turn Signal Rear Output Circuit Short To Ground

The ODBII code B1805 indicates a short circuit to ground in the rear turn signal output circuit, which can cause the turn signal to malfunction.

The severity of ODBII code B1805 is generally considered moderate.

Common Causes For: B1804 Lamp Turn Signal Rear Output Circuit Short To Battery

• Damaged wiring or connectors
• Shorted turn signal bulb
• Faulty turn signal relay
• Corroded or loose connections
• Faulty body control module (BCM)
• Water intrusion in the lighting circuit
• Incorrectly installed aftermarket lighting
• Grounding issues in the circuit

Common misdiagnosis for B1805 Lamp Turn Signal Rear Output Circuit Short To Ground

• Faulty turn signal switch
• Defective body control module (BCM)
• Damaged wiring or connectors
• Shorted or damaged bulbs
• Incorrectly installed aftermarket lighting
• Grounding issues in the circuit
• Faulty relay or fuse related to the turn signal system

Common Troubleshooting Steps

The OBD-II code B1805 indicates a problem with the rear turn signal output circuit, specifically a short to ground. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Visual Inspection:
• Check the wiring and connectors associated with the rear turn signal circuit for any visible damage, fraying, or corrosion.
• Inspect the turn signal bulbs to ensure they are not burnt out or improperly installed.
• Check for Short Circuits:
• Use a multimeter to check for continuity in the turn signal circuit. Disconnect the battery and the affected circuit, then check for continuity between the signal wire and ground. A reading of zero ohms indicates a short to ground.
• Inspect the wiring harness for pinched or damaged wires that could be causing a short.
• Test the Turn Signal Bulbs:
• Remove the rear turn signal bulbs and test them with a multimeter to ensure they are functioning correctly. Replace any faulty bulbs.
• Inspect the Turn Signal Relay:
• Check the turn signal relay for proper operation. A malfunctioning relay can cause issues in the circuit. Swap it with a known good relay if possible.
• Check the Ground Connections:
• Ensure that all ground connections related to the turn signal circuit are clean, tight, and free of corrosion. A poor ground can cause erratic behavior in the circuit.
• Scan for Additional Codes:
• Use an OBD-II scanner to check for any additional trouble codes that may provide more context or indicate related issues.
• Repair or Replace Damaged Components:
• If any damaged wiring, connectors, or components are found during the inspection, repair or replace them as necessary.
• Clear the Codes:
• After making repairs, clear the trouble codes using an OBD-II scanner and take the vehicle for a test drive to see if the code returns.
• Consult Wiring Diagrams:
• If the issue persists, consult the vehicle’s wiring diagrams to trace the circuit and identify any other potential issues.
• Professional Diagnosis:
• If you are unable to resolve the issue after these steps, consider seeking help from a professional mechanic who can perform more advanced diagnostics. By following these steps, you should be able to identify and resolve the issue causing the B1805 code.