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B1691 Autolamp Delay Circuit Short To Battery

The OBD2 code B1691 indicates a malfunction in the autolamp delay circuit, specifically a short circuit to the battery, which can prevent the automatic lighting system from functioning properly

Definition

The OBD2 code B1691 indicates a malfunction in the autolamp delay circuit, specifically a short circuit to the battery, which can prevent the automatic lighting system from functioning properly

Common causes

  • Shorted wiring or connectors in the autolamp circuit
  • Faulty autolamp relay
  • Defective body control module (BCM)
  • Corroded or damaged connectors
  • Malfunctioning headlight switch
  • Incorrectly installed aftermarket accessories

Common misdiagnoses

  • Faulty headlight switch
  • Defective body control module (BCM)
  • Shorted wiring harness
  • Malfunctioning relay
  • Bad ground connection
  • Incorrectly installed aftermarket lighting
  • Faulty autolamp sensor

Troubleshooting steps

  1. 1. Check the Vehicle's Manual

    Refer to the vehicle's service manual for specific information related to the Autolamp system and wiring diagrams

  2. 2. Visual Inspection

    Inspect the wiring and connectors associated with the Autolamp system for any signs of damage, corrosion, or loose connections

  3. 3. Look for frayed wires or any signs of short circuits

  4. 4. Check Fuses

    Locate and check the fuses related to the Autolamp system. A blown fuse may indicate an underlying issue

  5. 5. Test the Autolamp Relay

    If your vehicle uses a relay for the Autolamp system, test the relay to ensure it is functioning correctly. You can swap it with a similar relay in the fuse box to see if the problem persists

  6. 6. Inspect the Autolamp Sensor

    If your vehicle has a light sensor, check its operation. A malfunctioning sensor could cause the system to behave erratically

  7. 7. Check for Short Circuits

    Use a multimeter to check for continuity in the Autolamp circuit. Look for any shorts to ground or battery voltage

  8. 8. Disconnect the Autolamp module (if applicable) and check the wiring harness for shorts

  9. 9. Scan for Additional Codes

    Use an OBD-II scanner to check for any additional trouble codes that may provide more context to the issue

  10. 10. Inspect the Body Control Module (BCM)

    The BCM often controls the Autolamp function. Check for any faults in the BCM and ensure it is receiving the correct inputs and outputs

  11. 11. Perform a System Reset

    Sometimes, clearing the code and resetting the system can help. After clearing the code, take the vehicle for a test drive to see if the code returns

  12. 12. Consult Technical Service Bulletins (TSBs)

    Check for any TSBs related to the Autolamp system for your specific vehicle make and model. Manufacturers may have issued fixes for known issues.1

  13. 13. Professional Diagnosis

    If the issue persists after performing the above steps, consider seeking help from a professional mechanic or an automotive technician who has experience with electrical systems.Conclusion By following these troubleshooting steps, you should be able to identify the cause of the B1691 code and take appropriate action to resolve the issue. Always ensure safety precautions are taken when working with electrical systems in vehicles