P0572
PowertrainCruise Control/Brake Switch A Circuit Low
The brake light switch sits up behind the brake pedal and tells the ECU when you've got your foot on the brake. It feeds the cruise control, the brake lights, the auto gearbox shift-lock and a few other systems. P0572 means the ECU is seeing a voltage on that switch circuit that's lower than it should be, so it can't trust what the switch is reporting. The usual knock-on is dead cruise control and, on a bad day, brake lights that don't come on.
ⓘ Information only. This page provides general educational information about fault code P0572. 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 P0572 mean?
P0572 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Cruise Control/Brake Switch A Circuit Low.
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 kicks out the moment you set it
- • Brake lights stay dark when you press the pedal, or flicker on and off
- • Engine warning light on the dash, sometimes with no other obvious clue
- • Auto gearbox refuses to come out of Park because the shift-lock won't release
- • ABS or stability control warning lights joining in, since they share the brake signal
Possible causes
Causes commonly associated with P0572, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.
- 1. Faulty brake light switch itself, the most common cause and a cheap part on most cars
- 2. Brake switch knocked out of adjustment, often after pedal or clutch work, so it never reads a clean 'pedal up' or 'pedal down'
- 3. Chafed, pinched or broken wiring in the short loom running to the switch, especially where it flexes near the pedal box
- 4. Corroded or pushed-back pins in the switch connector giving a high-resistance, low-voltage reading
- 5. Blown fuse on the brake light or accessory circuit dragging the whole feed down
- 6. Water finding its way into the connector and causing intermittent dropouts that come and go with the weather
- 7. Failing Body Control Module or a poor earth, less common but worth checking once the simple stuff is clear
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. Have someone press the brake pedal while you watch the brake lights. No lights, or lazy lights, points you straight at the switch or its fuse before you touch the scanner.
- 2. Pull the codes properly and note anything alongside it. P0571 or P0573 sitting next to P0572 tells you the whole brake switch circuit is unhappy, not just one stuck signal.
- 3. Get up behind the pedal and look at the switch. Check it's clipped in square and hasn't drifted out of adjustment, then unplug the connector and check the pins for green corrosion or one that's been pushed back.
- 4. Back-probe the switch circuit with a multimeter. You're after roughly 5V at rest, climbing above 4.5V when the pedal goes down. A reading stuck low or jumping about confirms a circuit fault rather than a sensor that's simply worn.
- 5. Wiggle-test the loom near the pedal box while you watch the meter. If the voltage twitches, you've found a chafe or a broken strand hiding inside the insulation.
- 6. Check the relevant fuse last if you haven't already. A blown brake light or accessory fuse will drop the whole circuit and mimic a switch fault.
Common questions about P0572
What am I actually risking if I keep driving with this? +
The cruise control being dead is just annoying. The real worry is the brake lights. If this fault is stopping them coming on, the car behind has no warning when you slow down, and that's how you get rear-ended on a motorway slip road. On an auto you may also find yourself stuck in Park because the shift-lock won't free up. Get someone to check your brake lights today before you drive it any distance.
How quickly do I need to sort this? +
Treat it as a this-week job, sooner if your brake lights have stopped working. With working brake lights it's not an emergency, but the switch can degrade and start cutting your brake lights intermittently, which you won't always notice from the driver's seat. Don't let it sit for a couple of months hoping it clears. It rarely does, and an MOT tester will fail you on the spot if a brake light is out at the time of test.
Is it the switch itself or the wiring behind it? +
On most cars it's the switch. They're a simple mechanical part that wears out or drifts out of adjustment, and they're usually cheap, often £15 to £40 for the part. Wiring and connector faults do happen, normally corroded pins or a chafed loom near the pedal box, but they're the second thing to check, not the first. Swapping the switch fixes a good share of P0572s, so confirm the cheap part is healthy before you go chasing the loom.
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 →