B1685 – Lamp Dome Input Circuit Failure

The ODBII code B1685 indicates a failure in the lamp dome input circuit, which typically relates to issues with the interior lighting system, such as a malfunctioning switch or wiring problem affecting the dome light operation.

The severity of ODBII code B1685 Lamp Dome Input Circuit Failure is generally considered moderate.

Common Causes For: B1684 Mirror Driver/Passenger Switch Circuit Open

• Faulty dome lamp switch
• Shorted or open wiring in the dome lamp circuit
• Corroded or poor connections in the circuit
• Defective body control module (BCM)
• Malfunctioning dome lamp
• Blown fuse related to the dome lamp circuit
• Grounding issues in the circuit

Common misdiagnosis for B1685 Lamp Dome Input Circuit Failure

• Faulty body control module (BCM)
• Defective dome light switch
• Wiring issues or shorts in the circuit
• Malfunctioning door switches
• Faulty ground connections
• Incorrectly installed or damaged bulbs
• Issues with the vehicle’s electrical system or battery
• Software or programming errors in the BCM

Common Troubleshooting Steps

The OBD-II code B1685 refers to a “Lamp Dome Input Circuit Failure.” This code typically indicates a problem with the circuit that controls the dome light or interior lighting in a vehicle. 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 about the dome light circuit and wiring diagrams.
• Inspect the Dome Light Bulb: Ensure that the dome light bulb is functioning properly. Replace it if it is burnt out.
• Examine the Dome Light Switch: Check the dome light switch for proper operation. Ensure it is not stuck or malfunctioning.
• Inspect Wiring and Connectors: Look for damaged, frayed, or corroded wiring and connectors in the dome light circuit. Pay special attention to ground connections.
• Check Fuses: Inspect the fuses related to the interior lighting circuit. Replace any blown fuses.
• Test the Circuit: Use a multimeter to test the voltage and continuity in the dome light circuit. Check for proper voltage at the dome light and the switch.
• Scan for Additional Codes: Use an OBD-II scanner to check for any additional trouble codes that may provide more context for the issue.
• Inspect the Body Control Module (BCM): If the above steps do not resolve the issue, the Body Control Module (BCM) may be malfunctioning. Check for any software updates or faults in the BCM.
• Perform a Reset: Sometimes, clearing the code and resetting the vehicle’s computer can resolve the issue if it was a temporary glitch.
• Consult a Professional: If the problem persists after performing these steps, it may be best to consult a professional mechanic or technician for further diagnosis.Additional Tips: – Always disconnect the battery before working on electrical components to avoid short circuits or shocks. – Document any changes or repairs made during the troubleshooting process for future reference. By following these steps, you should be able to identify and resolve the issue related to the B1685 code.