B1812 – Lamp Backup Switch Input Circuit Short To Battery

The ODBII code B1812 indicates a malfunction in the backup lamp switch input circuit, specifically that there is a short circuit to the battery, which may cause the backup lights to operate incorrectly.

The severity of ODBII code B1812 is moderate.

Common Causes For: B1811 Lamp Backup Switch Input Circuit Open

• Shorted wiring or connectors
• Faulty backup lamp switch
• Corroded or damaged electrical connections
• Malfunctioning body control module (BCM)
• Incorrectly installed or damaged aftermarket accessories
• Grounding issues in the circuit

Common misdiagnosis for B1812 Lamp Backup Switch Input Circuit Short To Battery

• Faulty backup lamp switch
• Wiring harness issues
• Shorted wiring
• Faulty body control module (BCM)
• Defective backup lamps
• Grounding issues
• Incorrectly installed or damaged connectors

Common Troubleshooting Steps

The OBD-II code B1812 indicates a problem with the backup lamp switch input circuit, specifically a short to battery. This code is often related to the vehicle’s reverse lights and can be triggered by various issues. Here are some common troubleshooting steps to diagnose and resolve the B1812 code:

• Visual Inspection: **Wiring and Connectors: Inspect the wiring harness and connectors associated with the backup lamp switch. Look for any signs of damage, fraying, or corrosion.
• **Switch Condition: Check the backup lamp switch itself for any physical damage or wear.
• Check for Short Circuits: **Multimeter Testing: Use a multimeter to check for continuity in the wiring. Disconnect the battery and the backup lamp switch, then test the circuit for any shorts to ground or battery voltage.
• **Inspect Ground Connections: Ensure that all ground connections are secure and free of corrosion.
• Test the Backup Lamp Switch: **Functionality Test: With the switch disconnected, test it for proper operation. You can do this by checking for continuity when the switch is activated (in reverse).
• **Replace if Necessary: If the switch is faulty, replace it with a new one.
• Check the Backup Lamps: **Bulb Condition: Inspect the backup light bulbs to ensure they are functioning correctly. Replace any burnt-out bulbs.
• **Wiring to Bulbs: Check the wiring leading to the backup lamps for any signs of damage or shorts.
• Scan for Additional Codes: **Check for Other Codes: Use an OBD-II scanner to check for any additional trouble codes that may provide more context to the issue.
• Clear Codes and Test Drive: **Clear the Code: After performing the above checks and repairs, clear the B1812 code using an OBD-II scanner.
• **Test Drive: Take the vehicle for a test drive to see if the code reappears. Monitor the backup lights to ensure they function correctly.
• Consult Wiring Diagrams: **Refer to Service Manual: If the issue persists, consult the vehicle’s service manual for wiring diagrams and specific troubleshooting procedures related to the backup lamp switch circuit.
• Professional Diagnosis: **Seek Help if Needed: If you are unable to resolve the issue after these steps, consider seeking assistance from a professional mechanic or automotive technician who can perform more in-depth diagnostics. By following these steps, you should be able to identify and resolve the issue causing the B1812 code. Always ensure safety precautions are taken when working on electrical systems in vehicles.