Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P0571 Brake Switch A Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Brake switch A is the brake light switch or its signal to the engine module. The module needs it to cancel cruise control and for brake-throttle override, stop-start, idle control and the shift interlock. As cruise control is simply switched off, CARB treats such faults as emission-neutral – usually without warning lamp. P0571 is the general fault, usually detected by plausibility: Saab's 3.0 TiD (Bosch) sets it when the car brakes three times from over 49 km/h to standstill at 1.6 m/s² or more without a switch signal; Bosch EDC16 then switches cruise control off. NHTSA found Hyundai and Kia setting P0571 with P0504 from misadjusted brake light switches. Ford and GM petrol engines use P0572/P0573 instead.

Likely causes

Brake light switch misadjusted
Brake light switch faulty (worn contact)
Connector, wire or brake light fuse
Engine or body module

Symptoms

  • Cruise control cannot be set or switches off
  • Brake lights not working or permanently on
  • Possibly ABS/ESC warning (Hyundai/Kia)

Repair estimate

DifficultyEasyDIY possible
Parts and labour€15–120
Time0.3–1 h

Typical range across vehicles; the real cost depends on what the testing finds.

What to check first

  1. Check brake lights
  2. Inspect switch adjustment
  3. Check switch signals on a scan tool

Parts involved

brake switchbrake light fuseswitch wiringengine control module

Related codes

P0572P0573P0504P0703

References: saabwisonline.com, saabwisonline.com, static.nhtsa.gov, law.cornell.edu.