Brake Light Switch Circuit Fault
The system has detected a fault in the brake light 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 light switch is a small switch that turns on the brake lights when you press the brake pedal. If it fails, the lights may not work, and it can cause issues with systems that depend on brake light signals like cruise control.
What the computer is actually seeing
The engine control module (ECM) expects a specific voltage from the brake light switch when the brake pedal is engaged. It sees either no voltage when the pedal is pressed or fluctuating voltages.
What a healthy reading looks like
When the brake pedal is not pressed, voltage should be around 12V. When pressed, voltage should drop or stay near 0V, indicating the switch is closed.
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 brake light operation: Press the brake pedal and see if the brake lights illuminate. If they don’t, go to step 2. Decision: If lights are not working, switch may be faulty; if lights work, check wiring.
- 22. Inspect wiring and connectors for damage or corrosion, particularly at the brake switch. Decision: If damaged, repair/replace wiring; if okay, proceed to step 3.
- 33. Measure voltage at the brake light switch connector. With the pedal not pressed, it should read around 12V. Decision: If no voltage, check the circuit integrity; if voltage is present, switch may be faulty.
Common causes
- Faulty brake light switch
- Wiring issues (open circuit or short)
- Bad ground connection to the ECM or switch
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's best to fix this soon since it may impact brake light functionality, which is essential for safety.
What happens if I ignore this?
Ignoring this can lead to brake light failures, affecting your ability to signal stops to other drivers.
Does it relate to cruise control issues?
Yes, a faulty brake light switch can also affect cruise control operation, causing it to deactivate unexpectedly.
Working a real vehicle right now?
Let DiagCoach walk you through it live with your specific symptoms, vehicle, and what you've already checked.
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