# P0571: Brake Switch "A" Circuit

**Verdict:** Drive to a shop this week

Speed and idle control - Generic OBD-II code, applies to all gasoline cars and light trucks sold in the US since 1996.

- **Typical cost:** $50-$400
- **Urgency:** This week
- **Most likely:** Worn or misadjusted brake light switch
- **DIY?:** Often yes, easy

## Quick answer

P0571 means the computer has a problem with the signal from the brake switch, the switch above the brake pedal that tells the car you are braking. Cruise control usually stops working, and on some cars the brake lights, shift lock, or push-button start are affected too. A worn or misadjusted brake light switch is the usual cause.

## What does P0571 mean?

The brake switch, usually called the brake light switch, sits on a bracket above the brake pedal and changes state when you press the pedal. Besides turning on the brake lights, it tells the engine computer and other modules that you are braking. That signal cancels cruise control, lets the shifter leave Park, allows push-button cars to start, and feeds stability control and automatic engine stop-start on vehicles that have them.

Many vehicles use a switch with two circuits, labeled A and B, that switch in opposite directions so the computer can cross-check them. P0571 sets when the brake switch A signal is missing, stuck, or disagrees with the other circuit or with what the computer expects, and on some vehicles when the car slows hard with no brake signal. Which circuit is "A" and how the test runs differ by maker, and cruise control usually stays disabled until the fault clears.

## What are the symptoms of P0571?

- Cruise control will not set, or cancels on its own
- Brake lights stay on all the time, or do not come on
- Shifter will not come out of Park on some cars
- Push-button start car will not crank on some models
- Check engine light, and sometimes ABS or stability control lights

## What causes P0571?

Ranked from most to least likely. Check them in this order: the cheap, common causes first.

1. **Failed brake light switch** (most common). The switch is pressed thousands of times a year, and its contacts wear or stick, especially on older vehicles. One circuit can fail while the other still works, so the brake lights may act normally while cruise control quits. Watching the switch status on a scan tool, or with a test light, as you press the pedal confirms it.
2. **Misadjusted switch or broken pedal stopper** (common). If the switch sits too far from the pedal arm, it may not change state, and if it sits too close, it may never release. On some vehicles a small rubber or plastic bumper on the pedal arm breaks or falls out, letting the plunger travel too far. A flashlight under the dash often shows the missing piece.
3. **Blown fuse or wiring fault** (common). The switch circuits share fuses with other items on many vehicles, so a blown fuse can kill the brake lights and the brake signal together. Chafed wires near the pedal, a loose connector, or a short in a lamp socket can also corrupt the signal. Checking for power at the switch with the pedal up and down narrows it quickly.
4. **Brake lamp or LED bulb problem** (less common). On some vehicles the computer reads the brake signal through the brake lamp circuit, so burned-out bulbs, a bad socket, or a trailer wiring fault can set P0571. Aftermarket LED bulbs that draw far less current than the original bulbs can also confuse lamp monitoring. Check every brake light, including the high center light, before buying parts.
5. **Module fault or software issue** (rare). Rarely, the module that reads the switch has an internal fault or needs a software update. Depending on the vehicle, that may be the engine computer, the body module, or the ABS module. A shop confirms good signals at the module connector first, and checks for recalls and service bulletins before recommending an expensive module.

## How do you diagnose P0571?

1. Have someone watch all brake lights, including the center light, as you press and release the pedal.
2. Read codes in all modules and watch both brake switch inputs on a scan tool while pressing the pedal.
3. Inspect the switch adjustment, its plunger, and the pedal stopper bumper under the dash.
4. Check the fuses, then test power and signal at the switch connector with the pedal up and down.
5. Check for open recalls on your VIN before replacing parts.

## How do you fix P0571, and what does it cost?

| Fix | Typical cost | What it involves |
| --- | --- | --- |
| Adjust switch or replace pedal stopper | $50-$150 | A small part, but the switch must be set to the correct position. |
| Replace brake light switch | $80-$250 | Includes adjustment; some switches self-adjust and others need a set gap. |
| Repair wiring, fuse, or lamp socket | $100-$400 | Depends on how hard the fault is to trace. |

## Is it safe to drive with P0571?

> **Drive to a shop this week.** Driving is usually safe if your brake lights work, though cruise control may not. If the brake lights stay off when you press the pedal, other drivers cannot see you stopping, so avoid driving until it is fixed; if they stay on, they can drain the battery overnight.

## Will P0571 fail an emissions test?

Whether P0571 turns on the check engine light depends on the vehicle; on some it only disables cruise control. If the light is on, the car fails an OBD-II emissions test in most states. Many state safety inspections also check brake lights, so lamps that stay off or stay on can fail that test too.

## After the repair: clearing P0571

After the repair, clear the code and confirm on a scan tool that the brake switch changes state cleanly every time you press and release the pedal. Then test drive, set the cruise control, tap the brake, and make sure it cancels. Check that the brake lights turn off with the pedal released and the code stays away.

## How to prevent P0571

- Ask someone to check all brake lights every few months, or back up to a reflective window.
- Replace a broken pedal stopper bumper promptly so the switch plunger is not damaged.
- Choose LED replacement bulbs made for your vehicle, or ask whether lamp monitoring needs resistors.
- Have trailer wiring installed with a proper converter so it cannot back-feed the brake circuit.
- Fix brake lights that stay on right away, since they can drain the battery overnight.

## P0571 by make

| Make | What to know |
| --- | --- |
| Hyundai and Kia | Hyundai and Kia recalled brake light switches on a number of 2007 to 2011 models, so check your VIN for an open recall before paying for a switch. |

## Codes often seen with P0571

- [P0500](/codes/p0500): Vehicle Speed Sensor "A"
- [P0562](/codes/p0562): System Voltage Low

## Frequently asked questions

### Can I drive with a P0571 code?

Usually yes, as long as your brake lights work when you press the pedal. Cruise control will often be disabled, and some cars may not leave Park or start normally. If the brake lights do not come on, get it fixed before driving, because drivers behind you cannot see you stopping.

### What does the brake switch have to do with cruise control?

The brake switch tells the cruise control to cancel the moment you touch the brake pedal. If the computer cannot trust that signal, it disables cruise as a safety measure, because cruise that the brake cannot cancel would be dangerous. That is why P0571 so often shows up as cruise control not working.

### How much does it cost to fix P0571?

Most P0571 repairs cost $50 to $400 at an independent shop. Adjusting the switch or replacing a broken pedal stopper runs about $50 to $150, and a new brake light switch $80 to $250. Wiring, fuse, or socket repairs cost $100 to $400, depending on how hard the fault is to find.

### Can I replace a brake light switch myself?

Yes, on many vehicles it is an easy job with basic tools, done while lying under the dash. The switch usually twists or clips into a bracket above the pedal. The tricky part is adjustment, since some switches self-adjust and others need an exact gap, so follow your vehicle's procedure.

### Why won't my car come out of Park?

On most automatics, the shifter stays locked in Park until the computer sees the brake pedal pressed. If the brake switch signal is missing, the shift interlock never releases. Many vehicles have a small override slot near the shifter, described in the owner's manual, that lets you move it in an emergency.

### Why are my brake lights stuck on?

Brake lights that stay on usually mean the switch is stuck closed or out of adjustment, or a pedal stopper bumper has broken. The pedal arm then never pushes the plunger in fully. Fix it quickly, since lights stuck on confuse other drivers and can drain the battery overnight.

### Can a bad brake switch stop my car from starting?

Yes, on many push-button start vehicles the starter will not crank unless the computer sees the brake pedal pressed. A failed brake switch can make it seem as if the battery is dead even though the dash lights work. Check whether the brake lights come on when you press the pedal.

### Does P0571 affect how the brakes work?

No, P0571 does not change how hard the brakes work, because the switch is electrical and the brakes are hydraulic. It can still affect safety through the brake lights, and on some vehicles stability control or automatic stop-start may be limited. Pedal feel and stopping power should be unchanged.

### Will P0571 fail inspection?

It depends on the vehicle and the state. If P0571 turns on the check engine light, the car fails an OBD-II emissions test in most states. A safety inspection that checks brake lights will also fail the car if any brake light stays off or stays on, regardless of codes.

### Is P0571 covered by a recall?

Sometimes. Hyundai and Kia recalled brake light switches on many 2007 to 2011 models, and other makers have issued service bulletins on switches or pedal stoppers. Enter your 17-digit VIN on the NHTSA recalls site, since an open recall is repaired free at a dealer regardless of mileage.

## Sources

- [SAE J2012: Diagnostic Trouble Code Definitions](https://www.sae.org/standards/content/j2012_201812/)
- [NHTSA: Check for recalls by VIN](https://www.nhtsa.gov/recalls)

## Other speed and idle control codes

- [P0500 Vehicle Speed Sensor "A"](https://diagxcar.com/codes/p0500)
- [P0505 Idle Air Control System](https://diagxcar.com/codes/p0505)
- [P0506 Idle Air Control System RPM Lower Than Expected](https://diagxcar.com/codes/p0506)
- [P0507 Idle Air Control System RPM Higher Than Expected](https://diagxcar.com/codes/p0507)
- [P0520 Engine Oil Pressure Sensor/Switch "A" Circuit](https://diagxcar.com/codes/p0520)
- [P0521 Engine Oil Pressure Sensor/Switch "A" Circuit Range/Performance](https://diagxcar.com/codes/p0521)
- [P0522 Engine Oil Pressure Sensor/Switch "A" Circuit Low](https://diagxcar.com/codes/p0522)
- [P0523 Engine Oil Pressure Sensor/Switch "A" Circuit High](https://diagxcar.com/codes/p0523)
- [P0524 Engine Oil Pressure Too Low](https://diagxcar.com/codes/p0524)
- [P0562 System Voltage Low](https://diagxcar.com/codes/p0562)

## Symptoms

- [Why won't my car start?](https://diagxcar.com/symptoms/car-wont-start)

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Source page: https://diagxcar.com/codes/p0571
Updated: 2026-11-03
General information, not a substitute for a qualified mechanic.