B1807 – Lamp Tail Output Circuit Open

The ODBII code B1807 indicates that there is an open circuit in the tail lamp output circuit, meaning the system is not detecting the expected electrical connection or signal for the tail lights.

The severity of ODBII code B1807 is moderate.

Common Causes For: B1806 Lamp Tail Output Circuit Failure

• Open circuit in the tail lamp wiring
• Faulty tail lamp bulb
• Corroded or damaged connectors
• Defective tail lamp assembly
• Faulty body control module (BCM)
• Poor ground connection
• Damaged wiring harness

Common misdiagnosis for B1807 Lamp Tail Output Circuit Open

• Faulty tail light bulbs
• Bad tail light sockets
• Damaged wiring or connectors
• Faulty body control module (BCM)
• Incorrectly installed or loose connections
• Issues with the vehicle’s ground connections
• Malfunctioning switch or relay related to the tail lights

Common Troubleshooting Steps

The OBD-II code B1807 refers to a problem with the tail lamp output circuit, indicating that there is an open circuit in the tail lamp output. Here are some common troubleshooting steps to diagnose and resolve this issue:

• Check the Vehicle’s Manual: Refer to the vehicle’s service manual for specific information regarding the B1807 code and the tail lamp circuit layout.
• Visual Inspection:
• Inspect the tail lamp assembly for any visible damage or corrosion.
• Check the wiring harness and connectors for signs of wear, fraying, or disconnection.
• Ensure that the tail lamp bulbs are properly seated and not burnt out.
• Test the Tail Lamp Bulbs:
• Remove the tail lamp bulbs and test them with a multimeter or replace them with known good bulbs to ensure they are functioning properly.
• Check Fuses:
• Locate the fuse box and check for any blown fuses related to the tail lamp circuit. Replace any blown fuses and retest.
• Inspect the Wiring:
• Use a multimeter to check for continuity in the tail lamp circuit wiring. Look for any breaks or shorts in the wires.
• Check for proper grounding at the tail lamp assembly. A poor ground connection can cause circuit issues.
• Test the Tail Lamp Relay:
• If applicable, test the tail lamp relay to ensure it is functioning correctly. Replace it if necessary.
• Scan for Additional Codes:
• Use an OBD-II scanner to check for any additional trouble codes that may provide more context to the issue.
• Check the Body Control Module (BCM):
• If all other components are functioning correctly, the issue may lie within the BCM. Check for any software updates or faults in the module.
• Perform a Circuit Test:
• With the vehicle in the “on” position, use a multimeter to check for voltage at the tail lamp connector. If there is no voltage, trace the circuit back to find the open.
• Consult a Professional:
• If the issue persists after performing these steps, it may be best to consult a professional mechanic or technician who has experience with electrical systems and OBD-II diagnostics. By following these steps, you should be able to identify and resolve the issue related to the B1807 code.