P0572
Brake Switch A Circuit Low.
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 5
- AreaVehicle speed, idle control and auxiliary inputs
- 72
- FaultThe specific fault in that area
What it means
P0572 is the generic code for a low signal in the brake switch A circuit. The engine control unit monitors the voltage from the brake pedal switch, which tells it when the brakes are applied, and it has seen a voltage lower than expected. This can mean a wiring fault, a failed switch or a poor connection, and it often affects cruise control and brake light operation.
Symptoms
- Cruise control not working or cancelling unexpectedly
- Brake lights not working, or staying on all the time
- Engine warning light on
- Difficulty starting or shift lock problems on some models
- Reduced engine power or limited idle control on some models
- Brake light warning message on the dash on some models
Possible causes
- Faulty or misadjusted brake pedal switchlikely
- Switch not aligned correctly with the pedal, or pedal stop or plunger worn or brokenlikely
- Damaged, chafed or corroded wiring in the brake switch circuit, including a short to groundpossible
- Corroded or loose connector at the switch or control unitpossible
- Blown brake light or switch circuit fusepossible
- Fault in the engine control unit or body control module inputrare
How to diagnose
- Read the stored codes and freeze frame data, and note whether other brake or cruise control codes are present.
- Check that the brake lights work properly when the pedal is pressed and go off when it is released.
- Inspect the brake switch, its plunger and the pedal stop for damage, wear and correct adjustment.
- Check the relevant fuse and the brake light bulbs.
- Inspect the switch wiring and connector for chafing, water ingress, corrosion and loose pins.
- Using live data, watch the brake switch status change as the pedal is pressed and released.
- Check the supply, signal and earth at the switch connector with a multimeter, following the wiring diagram for the model.
- Test the wiring for a short to ground or an open circuit between the switch and the control unit.
How to fix
- Replace the brake pedal switch and adjust it to the manufacturer's specification.
- Repair or replace the pedal stop or switch mounting if worn or broken.
- Repair damaged wiring or replace the harness section.
- Clean or replace corroded connectors and terminals.
- Replace blown fuses after finding out why they blew.
- Diagnose and, if confirmed faulty, repair or replace the control unit that reads the switch.
Can I keep driving?
Medium severity
The car can usually be driven short-term, but faulty brake lights are a safety and legal issue, so get it fixed soon. If the brake lights are not working properly, do not drive it until they are repaired.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.