If your ABS warning light stays on and the brake lights flicker, you might be asking what does p0571 mean. This OBD‑II code points to a brake switch B circuit fault that can disable ABS and cause brake lights to fail. Drivers often notice the issue after a battery disconnect or when the switch wiring gets damaged.
It’s a problem you’ll want to address before the next safety inspection.
According to SAE J1850, the brake switch B circuit must maintain 12 volts when the pedal is pressed, otherwise the ABS module logs P0571. Ignoring the code can leave you without proper braking feedback and may cause the ABS to stay off during hard stops. If you’re unsure which scanner to use, check our guide on choosing a scanner before you buy.
Let’s break down why this code matters and how to fix it.
Problem / Pain Point
P0571 flashes when the ABS module sees an open or short in the brake switch B circuit. You’ll notice the ABS light on and brake lights that may flicker or stay off. The fault disables ABS and can leave the brake lights non‑functional, which raises stopping distance and collision risk.
It often appears after a battery disconnect, a hit to the wiring, or a worn switch. Common signs are:
- ABS light illuminated
- Brake lights erratic or off
- Pedal feels spongy
- Scan tool shows P0571
If you see any of these, stop driving and scan the car with a proper OBD‑II tool. If the code is intermittent, keep a scanner handy and check the switch connector for corrosion after any rain. If the wiring looks intact and the switch tests good, the ABS module may need replacement.
Ignoring P0571 can lead to brake system failure and may violate safety inspection standards.
What Does P0571 Mean: Core Explanation
P0571 signals that the ABS module sees a problem in the brake switch B circuit, which monitors pedal position and brake lights. The code means the circuit is open or shorted, so the ABS can’t confirm the brakes are applied. The brake switch B sits on the pedal assembly and sends a voltage signal to the ABS.
If the signal is missing or wrong, ABS disables and brake lights may not work. This matches the NHTSA code description for a brake switch B malfunction.
Image source: Wikimedia Commons / Dmitry G (CC BY-SA)
Check the switch first: a multimeter should show continuity when the pedal is pressed. Then inspect the wiring harness for broken wires, loose connectors, or corrosion. If the harness looks good, the ABS control module may need reprogramming or replacement.
Also check for water intrusion in the connector, which can cause intermittent faults. For a quick guide on checking fluid levels, see our article on adding transmission fluid. After repairs, clear the code and test drive to confirm ABS and brake lights function.
If P0571 returns, repeat the inspection or have a shop replace the ABS module.
Risks & Safe Practices
Driving with P0571 active can be dangerous because ABS may stay off and brake lights may not work. If the brake lights stay off, other drivers won’t see you braking, increasing rear‑end crash risk. The code also means the ABS can’t verify pedal position, so you lose brake‑assist during hard stops.
That can extend stopping distance and make the car harder to control in emergencies.
Image source: Wikimedia Commons / PantheraLeo1359531 (CC BY-SA)
Safe practices: stop driving if brake lights are off, and get the car scanned with a proper OBD‑II tool. If you must move the car, have a recovery point attached and drive slowly to a shop. For a quick reference on towing safely, see our guide on recovery point.
If the code is intermittent, keep a scanner handy and check the switch connector for corrosion after any rain. Replace any damaged wiring before clearing the code and test driving. Ignoring P0571 can keep the ABS warning light on, which may cause a failed safety inspection in many states.
If you’re unsure about the wiring, have a professional inspect the ABS module and switch assembly. They can run a full diagnostic and replace parts if needed.
How to Fix & When to Get Help
Start by connecting a reliable OBD‑II scanner to read and clear P0571. If you don’t have a scanner, borrow one or visit a shop that can read the code. If you need a scanner, see our guide on choosing a scanner.
Next, inspect the brake switch B connector for corrosion, water, or loose pins. Test the switch with a multimeter: it should show continuity when the pedal is pressed. If the switch tests good, examine the wiring harness for broken wires or a short to ground.
A visual check often finds the fault before you order parts. If the wiring looks intact, the ABS control module may need reprogramming or replacement. After any repair, clear the code and take a short test drive to confirm ABS and brake lights work.
If you’re uncomfortable with wiring or don’t have a multimeter, get a professional mechanic to finish the job. They can run a full diagnostic and replace the ABS module if needed. If you’re unsure, a shop can also help with installing accessories like a light bar.
FAQs
Why does P0571 keep coming back after I clear it?
The code returns because the underlying fault, usually a damaged wire, corroded connector, or a failing switch, has not been fixed. Clearing the code without repairing the circuit will make it reappear. Make sure to test the switch with a multimeter and inspect the harness for shorts before clearing again.
Can I drive with P0571 active?
You can drive, but ABS will stay off and brake lights may not work, which is unsafe. If the brake lights are off, have a recovery point attached and drive slowly to a repair shop. Avoid hard braking and get the issue fixed as soon as possible.
Do I need to replace the ABS module?
Only if the switch and wiring test good. A faulty switch or broken wire is the most common cause and is cheaper to replace. If the wiring is fine and the switch works, the ABS module may need reprogramming or replacement.
How much does it cost to fix P0571?
Typical repair costs range from $100 for a switch replacement to $300, $500 for wiring repair or ABS module replacement. Labor is usually 0.5, 1.5 hours, and parts vary by vehicle make. Check your vehicle’s service manual for exact part numbers.
Will P0571 affect my safety inspection?
Yes, many states require ABS and brake lights to function for inspection. A persistent P0571 can cause a failed inspection until the issue is resolved. Fixing the code and clearing it before the inspection will help.
If you need to transport the car while it’s not fixed, see our guide on building ramps for safe loading.
