Brake Light Switch Circuit
The brake light switch circuit is malfunctioning or out of range.
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 light switch isn't working properly, which means your brake lights may not be turning on when you press the pedal.
What the computer is actually seeing
The ECU expects the brake light switch to close (send a signal) when the brake pedal is pressed, usually around 0.5 volts when closed and near battery voltage (12-14 volts) when open. If it doesn't see these values correctly, it triggers this fault code.
What a healthy reading looks like
0.5V when the pedal is pressed, 12-14V when 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. Check the physical condition of the brake light switch and its connection. Any broken tabs, corrosion, or damage?
- 22. Inspect the wiring leading to the brake light switch for frayed insulation or damage. Is it intact?
- 33. Use a multimeter to check the voltage at the brake light switch connector. Do you see 12-14 volts when the brake pedal is not pressed? Yes - check for a faulty switch. No - look for wiring issues or a blown fuse.
- 44. While checking the switch, press the pedal. Do you see around 0.5 volts at the switch connector? Yes - switch is likely ok, continue checking wiring. No - the switch is likely faulty.
Common causes
- Faulty brake light switch
- Wiring issues in the brake light circuit
- Corroded connectors
- Blown fuse in the brake light circuit
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It's drivable but watch your brake lights; if they don't work, it might be a safety issue.
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 SPN codes?
Because multiple systems may share wiring or components, and one fault can affect others.
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 →