B3903 Code - Stop Lamp Relay Circuit Short
Quick Answer
The Body Control Module (BCM) supplies voltage to the Center High Mount Stop Lamp (CHMSL) and the Powertrain Control Module (PCM) when the stop lamps are active. Common causes include Faulty Stop Lamp Relay, Stop Lamp Relay harness is open or shorted, Stop Lamp Relay circuit poor electrical connection. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- B3903 indicates Stop Lamp Relay Circuit Short.
- Common causes
- Common causes include Faulty Stop Lamp Relay, Stop Lamp Relay harness is open or shorted, Stop Lamp Relay circuit poor electrical connection.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code B3903 Description
What are the Possible Causes of the DTC B3903?
- Faulty Stop Lamp Relay
- Stop Lamp Relay harness is open or shorted
- Stop Lamp Relay circuit poor electrical connection
- Faulty Body Control Module (BCM)
How to Fix the DTC B3903?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
B3903 05 Stop Lamp Relay Circuit Short to Battery or Open
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the B3903 code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Information for Specific Makes
- B3903 Buick — Stop Lamp Relay Circuit Short
- B3903 Cadillac — Stop Lamp Relay Circuit Short
- B3903 Chevrolet — Stop Lamp Relay Circuit Short
- B3903 GMC — Stop Lamp Relay Circuit Short
- B3903 Pontiac — Stop Lamp Relay Circuit Short
- B3903 Saturn — Stop Lamp Relay Circuit Short
Frequently Asked Questions about B3903 Code
1. What does the OBDII code B3903 mean?
Code B3903 indicates a short circuit in the stop lamp relay circuit, which affects the functionality of the vehicle's brake lights.
2. What are the common symptoms of code B3903?
Symptoms include non-functional brake lights, illuminated warning lights on the dashboard, and possible failure of cruise control to engage.
3. What causes the B3903 code?
Common causes include a shorted or damaged stop lamp relay, faulty wiring or connectors in the brake light circuit, or a malfunction in the brake light switch.
4. Can I drive with a B3903 code?
It's not advisable as non-functional brake lights pose a serious safety risk to you and other drivers on the road.
5. How do I diagnose a B3903 code?
Diagnosis involves inspecting the stop lamp relay, checking wiring and connectors for damage, and using a multimeter to test for shorts in the circuit.
6. How can I fix the B3903 code?
Repairs may include replacing the stop lamp relay, fixing damaged wiring or connectors, or replacing a faulty brake light switch.
7. How much does it cost to repair a B3903 code?
Costs vary depending on the issue but typically range from $50 to $200, including parts and labor.
8. Will clearing the B3903 code fix the problem?
Clearing the code without addressing the underlying issue will likely result in the code returning and the problem persisting.
9. Can a faulty brake light switch trigger the B3903 code?
Yes, a defective brake light switch can cause this code due to its role in completing the circuit for the stop lamp relay.
10. How do I prevent the B3903 code from occurring?
Regularly inspect and maintain the brake light system, including the relay, wiring, and switch, to prevent issues that could lead to this code.
Discuss the causes and fixes for B3903 OBDII Code
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