P0573
Brake Switch A Circuit High.
- 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
- 73
- FaultThe specific fault in that area
What it means
P0573 is the generic SAE J2012 code for a high signal in the brake switch 'A' circuit. The control unit saw the brake switch input reading high, or a brake state that did not make sense against other inputs such as vehicle speed or brake pressure. The brake switch tells the engine and cruise control systems when the pedal is pressed, so cruise control is usually affected first.
Symptoms
- Cruise control not working or cancelling itself
- Brake lights staying on or not coming on
- Engine warning light on
- Stored fault with no obvious driveability change
- Difficulty shifting out of park on some models
- Reduced or limited idle or throttle response on some models
Possible causes
- Faulty or misadjusted brake light switch at the pedallikely
- Damaged wiring, short to voltage or poor connector contact in the switch circuitlikely
- Brake pedal switch plunger position out of adjustment or pedal stop wornpossible
- Blown brake light fuse or faulty brake light bulb circuit affecting the signalpossible
- Fault in the body control module or other unit that processes the brake signalrare
- Software or calibration issue in the engine control unit where the manufacturer has a known faultrare
How to diagnose
- Read all stored codes and freeze frame data, noting what the vehicle was doing when the code set
- Check that the brake lights work properly and switch off fully when the pedal is released
- Inspect the brake switch, its plunger, the pedal stop and the connector for damage, corrosion or poor adjustment
- Check the relevant fuses and look over the wiring harness near the pedal for chafing or water ingress
- View the brake switch status in live data and compare it with the actual pedal position
- Test the switch for correct operation and resistance or voltage as per the model's wiring diagram, since switch type varies by vehicle
- Check the circuit for a short to voltage and for good earth and supply at the connector
- Check for manufacturer service information on software updates if everything else tests fine
How to fix
- Replace the brake switch and set it to the correct position
- Repair damaged wiring or clean and repair the connector terminals
- Replace the worn pedal stop or correct the pedal switch adjustment
- Replace the blown fuse after finding the cause of the failure
- Repair or replace the control unit that processes the signal if testing proves it faulty
- Apply a manufacturer calibration update only where a known fault is documented for the vehicle
Can I keep driving?
Medium severity
The car can usually be driven short term, but check that the brake lights work first, as faulty brake lights are unsafe and illegal. Book a repair soon, as cruise control and other functions may be unavailable until it is fixed.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.