P0571 Code: Brake Switch A Circuit — Causes & Fix
P0571 means a fault in the brake switch "A" circuit — the switch that tells modules when the brake pedal is pressed.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $20 – $250
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include a failed/misadjusted brake light switch, a blown fuse, or wiring faults. P0571 is a generic OBD-II powertrain code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer petrol car or light truck regardless of make. Fix the underlying fault, then clear the code with an OBD-II scan tool — it will return if the problem isn't resolved.
Symptoms
- Check engine light on
- Cruise control won't engage
- Brake lights or shift-lock issues
How to fix it
- 1
Check the brake light switch
1. Confirm the brake lights work and the switch is adjusted correctly. 2. Replace a faulty switch.
- 2
Inspect wiring/fuse
1. Check the switch connector and fuse. 2. Repair, then clear the code.
Frequently asked questions
Why won't my cruise control work with P0571?
Cruise control disengages using the brake switch signal. If that signal is unreliable, cruise won't engage until the switch is fixed.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.