B2520 – OBD-II DTC

OBD-II DTC B2520 – High Mount Stop Lamp Circuit Short to Battery

DTC B2520 meaning

DTC B2520 refers to a diagnostic trouble code indicating a “High Mount Stop Lamp Circuit Short to Battery.” This code is triggered when the vehicle’s onboard diagnostic system detects an electrical short in the high mount stop lamp circuit, which is responsible for illuminating the third brake light. This issue can lead to the high mount stop lamp being continuously illuminated or not functioning at all.

DTC B2520 symptoms

Common symptoms associated with DTC B2520 may include:

• High mount stop lamp remains on continuously.
• High mount stop lamp does not illuminate when brakes are applied.
• Illumination of the check engine light or brake warning light on the dashboard.
• Possible issues with other lighting circuits if they share a common ground.

DTC B2520 causes

Several factors can lead to the triggering of DTC B2520, including:

• Wiring issues such as frayed or damaged wires in the high mount stop lamp circuit.
• Corroded or poor connections at the high mount stop lamp or related connectors.
• Faulty high mount stop lamp assembly.
• Short circuits caused by moisture intrusion or physical damage.
• Malfunctioning brake light switch affecting the circuit.

DTC B2520 seriousness

DTC B2520 is considered a moderate to serious issue. While it may not immediately affect the vehicle’s drivability, it poses a safety risk as the high mount stop lamp is crucial for signaling braking to other drivers. A malfunctioning brake light can lead to accidents, making it important to address this code promptly.

How to diagnose DTC B2520

To diagnose DTC B2520, follow these steps:

1. Use an OBD-II scanner to confirm the presence of DTC B2520.
2. Inspect the high mount stop lamp for physical damage or burnt-out bulbs.
3. Check the wiring and connectors for signs of wear, corrosion, or shorts.
4. Test the brake light switch for proper operation.
5. Use a multimeter to check for continuity and voltage in the high mount stop lamp circuit.
6. Look for any additional DTCs that may provide further insight into the issue.

How to fix DTC B2520 step-by-step instructions

To fix DTC B2520, follow these steps:

1. Replace any burnt-out high mount stop lamp bulbs.
2. Repair or replace damaged wiring and connectors in the high mount stop lamp circuit.
3. Clean corroded connections to ensure good electrical contact.
4. Replace the high mount stop lamp assembly if it is faulty.
5. Test and, if necessary, replace the brake light switch.
6. Clear the DTC using an OBD-II scanner and test the system to ensure the issue is resolved.

How to erase DTC B2520

To erase DTC B2520, follow these steps:

1. Connect an OBD-II scanner to the vehicle’s diagnostic port.
2. Turn the ignition key to the “On” position without starting the engine.
3. Access the scanner’s menu and select the option to clear or erase trouble codes.
4. Confirm the action and wait for the scanner to complete the process.
5. Disconnect the scanner and start the vehicle to check if the code reappears.

Recommended tools for OBD-II diagnostics

Explore our expert picks: The Best OBD2 Scanners for 2025

Easy-to-use Multimeter for reliable diagnostics: AstroAI Auto-ranging Multimeter

Some of the links on this page may be affiliate links, which means we may earn a small commission if you make a purchase. This helps us keep our DTC database up to date and provide valuable content for free. We only recommend products that we have tested and believe to be the best in their class.