P0573
PowertrainCruise Control/Brake Switch A Circuit High
The brake light switch sits on the brake pedal arm and tells the ECU when you've pressed the brake. One of its jobs is to kill cruise control the moment your foot touches the pedal. P0573 means the ECU is seeing a higher voltage on that switch circuit than it should, so it stops trusting the signal. The usual result is dead cruise control, and on some cars the brake lights play up too.
ⓘ Information only. This page provides general educational information about fault code P0573. We do not assess the urgency or safety implications of any specific fault. That requires in-person diagnosis by a qualified mechanic. Full terms.
Recommended next steps
Whether a fault is urgent, drivable, or routine depends entirely on the cause on a specific vehicle, and that can only be determined by a qualified mechanic with diagnostic equipment. If a warning light is illuminated, the most reliable next step is professional diagnosis.
What does P0573 mean?
P0573 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cruise Control/Brake Switch A Circuit High.
This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.
Symptoms commonly associated with this code
Symptoms that drivers often report alongside this code. Not all may apply to every case:
- • Cruise control won't engage at all, or drops out for no reason
- • Set, resume and accelerate buttons do nothing when you press them
- • Engine warning light, though it can take a few drive cycles to show
- • Brake lights either don't come on with the pedal or stay on permanently
- • On some autos, the gear lever won't come out of Park because the shift interlock shares the brake switch signal
- • ABS or traction control light occasionally joining in
Possible causes
Causes commonly associated with P0573, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Failed brake light switch on the pedal arm, the most common cause by a mile. They're a cheap part that wears out or sticks
- 2. Brake switch knocked out of adjustment or worked loose, so the plunger isn't reading the pedal travel correctly
- 3. Chafed or shorted wiring in the switch circuit, often where the harness flexes behind the pedal box
- 4. Corroded or pushed-back pins in the switch connector, which throws the voltage readings off
- 5. Spilt drink or moisture getting into the switch or connector under the dash
- 6. Blown fuse on the brake or cruise circuit, less common but quick to check
How mechanics typically diagnose
A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.
- 1. Get someone to press the pedal and watch the brake lights. If they don't behave properly, you've found your starting point. The brake switch feeds both the lights and the cruise system
- 2. Pull all stored codes and look for P0571, P0572 or P0574 alongside it. Clear them, do a short test drive and see if P0573 comes straight back
- 3. Have a proper look at the switch where it bolts to the pedal arm. Check it's seated, the plunger contacts the pedal cleanly, and nothing's cracked or shifted
- 4. Unplug the connector and inspect the pins for green corrosion, spread terminals or damp. Reseat it and try again
- 5. Put a multimeter across the switch circuit and compare voltage and resistance to the workshop figures for your car. A reading stuck high points at a short to power or a duff switch
- 6. Check the relevant fuse last, and look up any service bulletins for your model since some makers issue updated switches
Common questions about P0573
How quickly do I need to sort this out? +
Sooner rather than later, mainly because of the brake lights. Losing cruise control is an inconvenience, but if this fault has your brake lights stuck off, the car behind has no warning when you slow down and that's an accident waiting to happen. If your brake lights still work normally with the pedal, it's less urgent and you can drive while you book it in. Either way, brake lights stuck on will flatten the battery and wear the bulbs, so don't sit on it.
Is it the switch itself or a wiring fault? +
Most of the time it's the switch. They're a small mechanical part on the pedal that takes thousands of presses and eventually sticks or wears, and a new one is usually £15 to £40. Before you condemn it, give the connector a wiggle and check the pins, because corroded or backed-out terminals fake a switch fault really convincingly. Actual harness damage is the least common of the three, but if a new switch and a clean connector don't fix it, that's where you go next.
How long does the repair take? +
If it's just the switch, a garage will have it done in well under an hour and you're often looking at £40 to £80 all in. A simple adjustment on an adjustable switch is a five minute job. Tracing a wiring short or a dodgy connector is where the time goes, anything from one to three hours of diagnostic labour depending on how buried the harness is, and the bill climbs to the £100 to £250 range once you add the fix.
Information only, not professional advice
The information on this page is provided for general guidance and educational purposes only. It is not a substitute for diagnosis or repair advice from a qualified mechanic. Always verify any fault before paying for repairs. carfaultcodes.co.uk accepts no liability for decisions made based on this information. Full terms →