B3903
Stop Lamp Relay Circuit Short
B3903 is an OBD-II diagnostic trouble code meaning: Stop Lamp Relay Circuit Short. Common causes: wiring harness damage, brake light relay malfunction. Estimated repair cost: $22–56.
Symptoms
- Brake lights don't work
- Brake lights flashing
- The malfunction indicator on the dashboard lights up
Causes
- Wiring harness damage
- Brake light relay malfunction
- Short circuit in the circuit
- Contact corrosion
- Problems with the control unit
How to Fix
- Check the integrity of the wiring harness
- Check the condition of the brake light relay
- Inspect contacts for corrosion
- Replace relay if necessary
- Repair or replace damaged wires
Related codes
Error B3903 by Vehicle Brand
FAQ
What does the B3903 code mean?
B3903 is an OBD-II diagnostic trouble code that indicates: Stop Lamp Relay Circuit Short
What causes a B3903 error code?
The most common causes of B3903 include: Wiring harness damage; Brake light relay malfunction; Short circuit in the circuit; Contact corrosion.
How do I fix a B3903 diagnostic trouble code?
To fix B3903: Check the integrity of the wiring harness. Check the condition of the brake light relay. Inspect contacts for corrosion. For a complete diagnosis, use an OBD-II scanner.
Is it safe to drive with B3903?
Do not drive — repair immediately
How much does it cost to fix B3903?
The estimated repair cost for B3903 is $22–56. Actual cost depends on your vehicle, location, and labor rates.
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