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B2520 High Mount Stop Lamp Circuit Short to Battery

The OBD2 code B2520 indicates a short circuit in the high mount stop lamp circuit, meaning there is an unintended connection to the battery, causing the stop lamp to malfunction

Definition

The OBD2 code B2520 indicates a short circuit in the high mount stop lamp circuit, meaning there is an unintended connection to the battery, causing the stop lamp to malfunction

Common causes

  • Shorted wiring or connectors in the high mount stop lamp circuit
  • Faulty high mount stop lamp assembly
  • Corroded or damaged connectors
  • Malfunctioning brake light switch
  • Grounding issues in the circuit
  • Incorrectly installed or damaged bulbs

Common misdiagnoses

  • Faulty brake light switch
  • Shorted wiring harness
  • Defective high mount stop lamp
  • Malfunctioning body control module (BCM)
  • Incorrectly installed or damaged fuses
  • Grounding issues
  • Faulty relay
  • Issues with the main wiring harness

Troubleshooting steps

  1. 1. Visual Inspection

    Check Wiring and Connectors: Inspect the wiring harness and connectors associated with the high mount stop lamp for any signs of damage, fraying, or corrosion. Look for any exposed wires that may be shorting to the battery or ground

  2. 2. Check the High Mount Stop Lamp

    Ensure that the high mount stop lamp itself is not damaged or improperly installed

  3. 3. Test the High Mount Stop Lamp

    Remove the Bulb: Take out the high mount stop lamp bulb and check for any signs of damage or a short circuit

  4. 4. Test the Bulb

    Use a multimeter to test the bulb for continuity. If the bulb is shorted, replace it

  5. 5. Check for Shorts

    Use a Multimeter: With the vehicle off, use a multimeter to check for continuity between the high mount stop lamp circuit and the battery positive terminal. A reading of zero ohms indicates a short

  6. 6. Inspect Ground Connections

    Check the ground connections for the high mount stop lamp circuit to ensure they are secure and free of corrosion

  7. 7. Inspect the Brake Light Switch

    Check the Brake Light Switch: The brake light switch may be malfunctioning or misadjusted, causing the circuit to remain closed. Inspect and test the switch for proper operation

  8. 8. Test for Continuity

    With the brake pedal pressed, check for continuity through the switch. If it remains closed when it shouldn't, replace the switch

  9. 9. Check the Fuse

    Inspect the Fuse: Locate the fuse for the high mount stop lamp circuit and check if it is blown. If it is, replace it and see if the issue persists

  10. 10. 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 or indicate related issues

  11. 11. Repair or Replace Components

    Repair Wiring: If you find any damaged wiring or connectors, repair or replace them as necessary

  12. 12. Replace Faulty Components

    If any components (bulb, brake light switch, etc.) are found to be faulty, replace them

  13. 13. Clear Codes and Test Drive

    Clear the Codes: After making repairs, clear the trouble codes using an OBD-II scanner

  14. 14. Test Drive

    Take the vehicle for a test drive to see if the code reappears and to ensure that the high mount stop lamp functions correctly

  15. 15. Consult a Professional

    If the issue persists after following these steps, it may be necessary to consult a professional mechanic for further diagnosis and repair. By following these troubleshooting steps, you should be able to identify and resolve the issue related to the B2520 code