ABS/TCS Brake Switch Circuit

What it means

The ABS module has detected an improper signal from the brake pedal switch, which tells it that the driver is pressing the brake. The module may disable traction control (TCS) and stability control, and brake lights and cruise control can be affected. Detection conditions vary by manufacturer.

Related codes: P0571U0121C0550U0415

Symptoms4

• ABS or traction control (TCS) light on.
• Rear brake lights not working or staying on.
• Cruise control not working.
• On some vehicles, the shift lever is hard to move out of park.

Possible causes5

• Faulty or misadjusted brake pedal switch.
• Blown brake light fuse.
• Burned-out brake light bulbs, since on some vehicles they affect the switch circuit.
• Corroded switch connector or damaged wiring.
• ABS module fault in rare cases.

How to diagnose5

1. First confirm all rear brake lights work when the pedal is pressed.
2. Watch the brake switch status on a scan tool while pressing and releasing; it should change immediately with pedal movement.
3. Check the brake light fuse and bulbs.
4. Check the switch adjustment and mounting at the pedal, and inspect its connector and wiring.
5. Compare the switch signal in the engine computer and the ABS module if the switch feeds both.

How to fix5

1. Replace the blown fuse or burned-out brake bulbs.
2. Adjust or remount the brake switch per the manufacturer specification.
3. Replace the brake switch if proven faulty.
4. Repair the damaged connector or wiring.
5. Clear the codes and confirm the brake lights and cruise control work and the warning lights stay off.

The cost is low for a fuse, bulb or switch adjustment, and reaches the upper end with a switch replacement and wiring repair.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions