P0724: Brake Switch B Circuit High
What to do
Check your brake lights immediately — have someone stand behind the car while you press the pedal. If they do not work, do not drive it until the switch is replaced. If the engine also stalls as you come to a stop and restarts straight away, that is the same fault rather than a separate engine problem.
What this code means
The brake switch signal reads as though the brake pedal is never applied. This is the opposite of P0719 and the more consequential of the two, because two systems that are supposed to react to braking now do not.
The transmission releases torque converter lock-up when you brake, so the engine is not dragged down as the vehicle stops. If it never learns the brake is applied, lock-up can stay engaged all the way to a standstill and the engine stalls — exactly as a manual does if you stop without pressing the clutch. An engine that dies every time you come to a junction, and restarts immediately, is describing this.
The first thing to check is the brake lights, because the same switch usually operates them. Driving without brake lights is both an offence and a genuine risk of being hit from behind, and it is the part of this fault that cannot wait.
Likely causes
Start here
- Faulty brake light switch · easy
Less common
- Open circuit in switch wiring · moderate
- Corroded or loose connector · easy
- Blown brake light fuse · easy
Symptoms
Components involved
Information, not instruction
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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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