P0573–P0724 Brake Switch A Circuit High

Which code is which

Same fault, different cylinder or bank — diagnosed the same way. Several set together usually means one shared cause.

The definition

P0573: Brake Switch A Circuit High.

P0573 is a powertrain code (the engine or gearbox), defined by the SAE standard - it means the same thing on any make of car, and any generic OBD-II reader will decode it.

What to check first

Cheapest and fastest checks first:

1. Unplug the sensor and check whether the signal falls. If it stays high, suspect the wiring rather than the sensor.
2. Check the earth path - a missing earth makes a sensor read high.

What actually causes this on a VAG

Same brake light switch as the code above, but here the signal is reading high or open - the ECU is seeing no connection where it expects one. In practice that usually means the switch or its circuit has failed in a way that stops the car being told your foot is on the brake. Cruise control will not engage, an automatic may refuse to shift out of Park, and on an automatic or any car with push-button start the engine may not start at all, because a confirmed brake pedal press is one of the starting conditions. Check the brake lights first: if they are not working, that is the urgent part of this fault, not the warning light.

Most likely causes, in order

1. Failed brake light switch, open circuit. The switch failing open is a common wear-out mode and matches this code exactly. Confirm it the same way as for the low-side code: watch the brake switch status in live data while the pedal is pressed - a failed-open switch simply never changes state.
2. Unplugged, loose or damaged connector. An open-circuit fault genuinely points at a broken connection more than at a worn contact, so check the plug at the pedal box early. Look for a connector knocked loose during footwell work, a broken locking tab, or a wire pulled out of the back of the plug. This costs nothing.
3. Blown fuse or broken supply to the switch. If the brake lights are dead as well as the code being present, check the relevant fuse before touching the switch. A single fault killing both is usually upstream of the switch rather than inside it.
4. Wiring break in the run from the pedal box. Less common, but a chafed or broken wire behind the trim will produce the same result. This is a job for someone with a meter and the wiring diagram rather than guesswork.

Worth knowing: If your brake lights are not working, the car is not safe or legal to drive - get that sorted before anything else, and do not treat this as a warning light you can leave for a few weeks. If the car will not start with this code stored, pressing the brake pedal firmly and repeatedly sometimes gets it to fire; treat that as a clue pointing at the switch rather than at the starting system. It is not a repair, and it tells you nothing about whether your brake lights are working.

Common questions

What does P0573 mean?

P0573 means Brake Switch A Circuit High. The voltage on this circuit is sitting near battery voltage. Typically a short to a positive feed, or a disconnected sensor floating high.

Can I drive with P0573?

This affects a system that helps you stop or stay straight. Assume ABS and stability control are reduced or switched off until it is fixed.

Related reading

• Several warning lights on at once: usually one cause, not many
• Humming or Whining Noise on a VW or Audi: How to Place It
• The 10-minute diagnostic check before you buy a used VW or Audi
• Why the same fault code has completely different causes