P0571: Cruise Control/Brake Switch A Circuit Malfunction

What does P0571 actually mean?

The computer is not seeing the expected signal from the brake pedal position switch that cruise control uses to cancel itself when the brake is pressed. On many vehicles this same switch also feeds the brake lights and torque converter lockup release, so this is not only a cruise control issue.

The code sits in the cruise control brake switch area and is reported by the comprehensive component monitor. It names the circuit or the condition where the computer saw a reading outside its expected range. It does not name a failed part, and several genuinely different faults set this same code, which is the whole reason the causes below are ordered rather than listed.

What people usually notice

• Cruise control will not engage or will not cancel properly
• Brake lights not working correctly
• Transmission does not release torque converter lockup when braking
• Engine feels like it wants to stall approaching a stop

Why does P0571 set?

The causes below are ordered by how often they turn out to be the answer, cheapest and most common first. That order matters more than the list itself: the expensive component named in the code text is very rarely the first thing to replace, and working down from the top is what stops a cruise control brake switch fault becoming an expensive guess.

Misadjusted or worn brake switch is the one to rule out before anything else. Very common and cheap to replace, this switch sits under the dash and takes constant pedal use.

The order worth checking on P0571

Start with freeze frame. There is limited useful freeze frame data here, check whether the brake switch state was stuck on or off when the code set. That snapshot is taken at the instant the code set, and it is the single most useful piece of evidence you have, which is also why clearing the code before reading it is such a costly habit.

This code is diagnosed by watching values change rather than by reading the number again, so the tool has to stream live data and hold freeze frame. Live data on the brake switch input while pressing the pedal shows whether the switch is transitioning correctly.

The order worth working in

• 1. Misadjusted or worn brake switch: Very common and cheap to replace, this switch sits under the dash and takes constant pedal use.
• 2. Corroded connector at the switch: A cheap and common cause to check before replacing the switch.
• 3. Broken wire near the pedal bracket: Repeated pedal movement can fatigue wiring at this point over years.
• 4. Blown fuse: A lost supply voltage will read as a switch circuit malfunction.
• 5. Failing switch internally: The switch mechanism itself wears out with high mileage.

Is it safe to drive with P0571?

Cruise control will likely be disabled, and because this switch is often shared with the brake lights, have it checked soon rather than assuming it is only a convenience feature.

This is a severity 2 of 4 code. It will not usually strand you, but it will fail an emissions test while it is present, and the underlying fault rarely gets cheaper by being left alone.

What does it cost to ignore P0571?

If the brake lights are affected, this becomes a real risk of a rear end collision, not just a lost convenience feature.

There is also the diagnostic cost of waiting. Freeze frame data, pending code history and the readiness monitor state all describe the fault as it was when it set, and all of it is lost the moment somebody clears the code to make the lamp go out.