B2504: Right Low Beam Circuit Short to Battery
The Body Control Module (BCM) has detected a short to battery voltage on the right front low beam control circuit. This code sets when the BCM commands the right low beam off but still senses voltage on the output circuit, indicating the wiring is shorted to a constant power source or the BCM's internal driver has failed in a high state.
1. Commonly Affected Makes
2. Most Common Causes
- Right low beam circuit wiring chafed or pinched, shorting to B+
- Right headlamp connector damaged, corroded, or with shorted pins
- Right headlamp module (if equipped) or ballast with internal short to battery
- BCM internal output driver failure (stuck high)
- Aftermarket accessory (alarm, LED lights) improperly wired, injecting voltage into the circuit
3. Symptoms You Will Notice
- Right low beam inoperative or stuck on
- Check Engine Light or Service Lamp Soon light illuminated
4. Step-by-Step Diagnosis
Verify the code and check for related BCM codes
Inspect right low beam circuit wiring for shorts to battery voltage
Check right headlamp connector for damage, corrosion, or shorted pins
Test right headlamp module/ballast for internal short (if applicable)
Disconnect aftermarket accessories and see if code clears
If all else is good, suspect BCM internal failure and test/replace BCM
5. Frequently Asked Questions
Is it safe to drive?▼
Yes, but the right low beam may not work or may stay on, which can reduce visibility and may cause a burned-out bulb or further electrical issues. It's best to diagnose and repair promptly.
How much does it cost to fix?▼
Repair costs vary widely: a simple wiring repair may cost $50-$150, while replacing a BCM can run $300-$800 including programming. Diagnosis typically adds $100-$150.