Brake Switch A Circuit 1 Fault
There’s a problem with the brake switch signal to the ECM.
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, which tells the engine computer when you’re braking, isn’t working right or is sending a bad signal.
What the computer is actually seeing
The ECM expects a specific voltage signal from the brake switch when it's pressed. When braking, it should see around 0 volts (ground), and when released, it should see around 12 volts. If the signal stays high or low when it shouldn't, it triggers this code.
What a healthy reading looks like
Brake switch should read close to 0V when braking and near 12V when not; there should be continuity in the circuit when pressed.
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.
- 1Check the brake switch wiring and connector for damage or corrosion.
- 2Test the brake switch: With the key on, check the voltage at the switch. It should show 12V when not pressed and drop to 0V when pressed.
- 3If the brake switch voltage is correct, check the signal at the ECM. If the switch is functioning but readings are incorrect at the ECM, suspect a wiring issue between the switch and the ECM.
- 4If the brake switch and wiring appear good, check for faults in the ECM that could be misreading the signal.
Common causes
- Faulty brake switch
- Wiring issues in the brake switch circuit
- Bad connector at the brake switch
- ECM problem with reading brake switch signal
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable but may affect braking systems that rely on a proper signal for features like cruise control.
Will the code return after I clear it?
If the issue is still present, it likely will return. Address the brake switch or wiring issues first.
Why does this code sometimes pair with other codes?
Related codes could involve other components that share the brake switch signal or systems that depend on it.
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 →