Service Brake Switch Circuit Fault
This code indicates a problem in the service brake switch circuit.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The brake switch is responsible for sending a signal to the computer when you press the brake pedal. If the switch is faulty or the circuit is interrupted, it can't tell when you're stopping.
What the computer is actually seeing
The brake light switch should show a closed circuit (0 volts) when the brake is applied and an open circuit (12 volts) when released. If the expected voltage levels aren't present, the computer sets this code.
What a healthy reading looks like
Closed circuit: 0 volts with brake pedal pressed; Open circuit: approx. 12 volts when brake pedal is released.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the brake switch for proper operation. Check if the brake lights illuminate when the pedal is pressed. If not, replace the switch.
- 22. Check the wiring and connectors at the brake switch for damage or corrosion. Repair any issues found.
- 33. Measure voltage at the brake switch connector. It should be 12 volts with the ignition on and brake pedal not pressed. If 12 volts is not present, trace back to the fuse and wiring harness for faults.
- 44. If all wiring is intact and the switch is new, check the body control module for faults.
Common causes
- Faulty brake switch
- Wiring issues in the brake switch circuit
- Corroded connectors
- Brake fluid leaks affecting switch operation
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's considered moderate severity; you can drive but should fix it soon as it affects braking system signals.
Will this code come back after clearing?
If the underlying issue isn't fixed, yes, it will likely return.
Why does this code pair with other codes?
Codes like C1257 and C1248 relate to brake system functionalities that rely on the same switch, hence their frequency together.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
Start guided diagnostic →