P0571 Code: Brake Switch A Circuit Malfunction
The engine computer doesn't trust the brake pedal switch signal – cruise control usually stops working.
Safety first · Consult a professional
- Braking system affected: ABS may be disabled. Drive carefully and have it checked promptly.
At a glance
Severity: Low
- Meaning
- Brake Switch A Circuit Malfunction
- System
- Speed & Idle Control · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $5–$250
- DIY difficulty
- Easy
The brake pedal switch sits at the top of the pedal arm under the dash. Most have two circuits: one switches the brake lights and tells the PCM the pedal is pressed, the other opens to cancel cruise control. The PCM also uses the signal to release the torque converter clutch, unlock the shifter, allow push-button starting and manage start-stop and brake-throttle override. P0571 means the 'A' circuit behaves implausibly rather than being stuck; many PCMs set it when the car slows from speed to a stop several times without ever seeing the brake signal, when the signal flickers, or when the two switch circuits disagree. Wear inside the switch and poor adjustment cause most cases.
Can I keep driving? The brakes themselves work normally, but confirm the brake lights work every time you press the pedal before driving. Expect cruise control and possibly start-stop to be unavailable until the switch is fixed.
How to read P0571
- P Powertrain
- 0 Generic (SAE)
- 5 Speed, idle & inputs
- 71 Specific fault
Symptoms
- Cruise control won't set or drops out for no reason
- Brake lights working only some of the time
- Shifter occasionally stuck in Park until the pedal is pressed harder
- Traction control or stability light on in some vehicles
- Start-stop system not shutting the engine off at lights
- Code may be stored without turning on the check engine light
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Worn brake switch with intermittent internal contacts
- Switch out of adjustment so it switches too late or inconsistently
- Worn or missing plastic stopper pad on the pedal arm
- Loose or corroded connector at the switch
- Stop lamp fuse, bulb or lamp circuit issue affecting the signal
- Wiring rubbed through near the pedal pivot
- PCM or body module input fault
Diagnosis step by step
Watch the brake lights
Have a helper watch, or back up to a wall or garage door, and press the pedal slowly and quickly several times. The lights should come on within the first bit of pedal travel every single time.
Tools: Flashlight
Read both switch states on the scan tool
Display brake switch A and B (sometimes called brake lamp and brake pedal/cruise) in live data. Pressing the pedal slowly, both should change almost together and in opposite directions; a delay, flicker or one that never changes points to the switch or its adjustment.
Tools: OBD-II scanner
Inspect the switch and pedal stopper
Look up under the dash with a light. The switch plunger should press against the pedal arm or a small stopper pad; a crumbled pad, cracked switch body or loose mounting clip changes the switching point.
Tools: Flashlight
Check the switch contacts with a meter
Unplug the switch and measure each circuit with the pedal released and pressed. Each should switch cleanly between near 0 ohms and open; readings that jump around while you move the plunger slowly confirm internal wear.
Tools: Multimeter
Adjust or replace the switch
Self-adjusting switches are usually set by inserting them with the pedal held down, then pulling the pedal up by hand; threaded types are set to a specified gap. Follow the procedure for your vehicle, then clear the code and test-drive with several stops from speed.
Tools: Screwdriver, Pliers
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace brake switch (including adjustment) | Yes | $50–$180 |
| Replace worn pedal stopper pad | Yes | $5–$60 |
| Repair connector or wiring at the pedal | No | $80–$250 |
| Diagnosis at a shop | No | $60–$150 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Emissions / smog test impact
Depends
P0571 often doesn't light the check engine light, so an OBD-II emissions test usually isn't affected. In states with safety inspections, brake lights that don't work reliably are a failure item.
Frequently asked questions
Why did a brake switch code kill my cruise control?
Cruise control must cancel the instant you touch the brake. If the PCM can't trust the brake signal, it disables cruise as a safety precaution until the fault is fixed.
The brake lights seem to work. Why is the switch still at fault?
P0571 is often intermittent or caused by a slow or late switching point. The lights may work when you check but fail to switch at the moment the PCM expects, for example during a gentle stop.
Is the brake switch hard to replace?
On most cars it is held by a twist-lock or clip above the pedal and takes little time, though working upside down under the dash is awkward. The important part is setting the adjustment correctly afterward.
Could a burned-out brake bulb cause this code?
On some vehicles the PCM monitors the brake lamp circuit through the bulbs, so a failed bulb or unsuitable LED replacement bulbs can disturb the signal. Check all brake bulbs, including the center high-mount light.