OBD-II Fault Code

B2520: High Mount Stop Lamp Circuit Short to Battery

Meaning, symptoms, likely causes, diagnostic checks and repair guidance for B2520.

System family

Body

Generic/SAE

Repair category

Lighting

Use this category to narrow your checks before replacing parts.

Severity

Medium

Severity is a general guide. Confirm with scan-tool data and vehicle symptoms.

What B2520 usually means

High Mount Stop Lamp Circuit Short to Battery.

Common symptoms

Body/accessory warning lamp or feature not working

Likely causes

Blown bulb/LED module; Poor ground; Fuse/relay fault; Switch/module/wiring issue; Wire shorted to power feed; Incorrectly repaired harness; Internal component short; High signal voltage; Open ground; Short to voltage; Failed sensor

Diagnostic checks

Check related fuses, connectors, grounds and switch/module power supply; Check bulb/module, fuse, ground and connector corrosion; Check for unwanted voltage on signal/control circuit; Check sensor ground and signal circuit for short to voltage

Repair guidance

Replace failed bulb/module, repair ground/wiring, replace switch/relay if confirmed; Repair harness short to power or replace internally shorted component; Repair ground/signal circuit or replace confirmed faulty sensor

Verification after repair

Operate the affected body/accessory system and rescan

Note: Confirm vehicle make/model/year because manufacturer-specific codes can vary. A DTC identifies a circuit or system condition, not always the failed part.