P0571: Cruise Control Brake Switch A Circuit
What to do
Check the brake lights work — get someone to look while you press the pedal. If they do not, the car is unsafe in traffic and needs immediate attention. Cruise control will refuse to engage until this is fixed, which is the system protecting you.
What this code means
A fault in the brake switch circuit as read by cruise control. The brake signal is the primary means by which cruise control is cancelled, so a module that cannot trust it will refuse to engage the system at all — which is correct and conservative behaviour rather than a secondary fault.
Because the same switch operates the brake lights, the first check is simply whether they work. A brake light that does not illuminate turns this from a cruise control inconvenience into a road safety fault.
Likely causes
Start here
- Faulty brake light switch · easy
- Corroded or loose connector · easy
Less common
- Blown brake light fuse · easy
Symptoms
Components involved
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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