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

P0573 Brake Switch A Circuit High

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. P0573 means the switch signal stays high – always pressed – although the car is not braking. Ford diesel checks over 40 accelerations, Ford petrol over 25 brake applications without warning lamp; GM in the Saab 9-4X compares the input with the body module, 8 of 10 samples over 2 s. Typical are a switch stuck closed, a pedal not fully returning or a short to positive. Cruise control is locked out.

Likely causes

Brake light switch stuck closed or misadjusted (pedal stop buffer missing)
Brake pedal not returning fully (floor mat, return spring)
Signal line shorted to positive
Body or engine module

Symptoms

  • Brake lights permanently on
  • Cruise control unusable
  • Shift interlock disturbed

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.

Parts involved

brake switchbrake light fuseswitch wiringengine control module

Related codes

P0571P0572P0504P057B

References: fordservicecontent.com, fordservicecontent.com, saabwisonline.com, saabwisonline.com.