P0571
Brake Switch A Circuit
Cruise control / brake switch
Generic OBD-II
Low
What it means
P0571 means the ECM has seen an implausible signal from the brake pedal switch, the switch that also feeds cruise control, the brake lights, and the shift interlock. It's most often a failed or misadjusted brake light switch. The car drives normally, but cruise control may be disabled and brake-light behaviour can be affected, which makes it a safety-relevant fix.
Low
Can I keep driving? Drivable — the engine runs fine, but cruise control may not work and the brake-light/shift-interlock functions can act up; fix it soon for safety and convenience.
Common symptoms
What you'll notice
- Cruise control won't set, or disengages on its own
- Brake lights that don't come on, stay on, or work erratically
- Shift interlock issue — can't move the shifter out of Park
- Check-engine light on
Common causes
Most likely first
- Faulty or misadjusted brake light switch (the most common cause)Likely
- Blown brake-light fuse or wiring fault in the switch circuitCommon
- Loose or corroded connector at the brake switchCommon
- Two brake switch inputs disagreeing (redundant switch signal mismatch)Less often
- Faulty engine control module (ECM), rareLess often
How to diagnose & fix
Work through it in order
- Inspect and test the brake light switch — confirm the brake lights work when the pedal is pressed.
- Check the brake-switch adjustment and the pedal striker; readjust if the switch isn't fully actuated.
- Check the brake-light fuse and the switch connector for damage or corrosion.
- Back-probe the switch signal to the ECM to confirm it changes state with the pedal.
- Replace the brake switch if it tests faulty. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0571?+
The engine and brakes still work, but faulty brake-light signaling is a safety issue — other drivers may not see you braking. Get the switch checked promptly.
Can I just clear P0571?+
It will return until the switch or its wiring is fixed. Many cars also block cruise control and shifting out of Park while this fault is active.
Related codes
Often seen with P0571
Read & clear P0571 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX