Brake Switch Circuit Input A Low
The brake switch circuit input A is reading a voltage that is too low.
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What it means (plain English)
The brake light switch is supposed to send a voltage signal to the computer when you press the brake pedal. If it's sending too low of a voltage, the system thinks you aren't applying the brakes when you are.
What the computer is actually seeing
When the brake switch is pressed, the signal voltage should be around 0.5V to 12V. If the voltage drops below the expected threshold, typically around 0V to 0.2V, it triggers the code.
What a healthy reading looks like
Brake switch signal voltage should be between 0.5V and 12V when activated.
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 brake fluid level; add fluid if low and check for leaks.
- 22. Inspect the wiring and connectors at the brake switch for damage or corrosion. Repair as necessary.
- 33. Measure the voltage at the brake switch connector; it should be between 0.5V and 12V when the brake pedal is pressed. If it's low, suspect a faulty switch.
- 44. If the switch tests okay, check the wiring continuity from the brake switch to the PCM. Use a multimeter to ensure there are no shorts or breaks.
- 55. If everything else checks out, replace the brake switch and clear the code.
Common causes
- Faulty brake switch
- Wiring issues such as shorts or opens
- Corroded connectors at the brake switch
- Problems in the vehicle's computer system
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's moderate severity; you can drive, but be aware that the brake light may not work, affecting driving safety.
Will this code come back after repairs?
If the underlying issue is fixed, it shouldn't return; however, monitor for any electrical issues.
Why does this code pair with C1507?
Both codes relate to issues with the brake switch circuit; they may originate from similar faults.
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