Faulty or misadjusted brake light switch (switch B contacts stuck or out of position); Brake pedal switch plunger or striker out of adjustment, or pedal stop worn or missing; Wiring fault such as a short to voltage on the brake switch B circuit; Corroded, damaged or loose connector at the brake switch; Blown fuse or fault in the brake lamp circuit affecting the signal; Fault in the engine or transmission control unit input circuit.

P0724

Brake Switch B Circuit High.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
7: AreaTransmission
24: FaultThe specific fault in that area

What it means

P0724 is the generic SAE J2012 code for Brake Switch B Circuit High. The control unit saw a signal from the second brake switch circuit that stayed high, or did not agree with the brake pedal state or the main brake switch. It is often set when the brake lamp switch, its wiring or the pedal position does not match what the control unit expects.

Symptoms

Engine warning light on
Brake lights stuck on or not working
Cruise control not working or cancelling
Automatic gearbox shift lock or key interlock not releasing
Torque converter clutch not engaging, or poor fuel economy
Engine idle or stall issues when stopping, on some models

Possible causes

Faulty or misadjusted brake light switch (switch B contacts stuck or out of position)likely
Brake pedal switch plunger or striker out of adjustment, or pedal stop worn or missinglikely
Wiring fault such as a short to voltage on the brake switch B circuitpossible
Corroded, damaged or loose connector at the brake switchpossible
Blown fuse or fault in the brake lamp circuit affecting the signalpossible
Fault in the engine or transmission control unit input circuitrare

How to diagnose

Read stored codes and freeze frame data, and note any other brake, cruise or lamp-related codes
Check whether the brake lights work correctly and switch off fully when the pedal is released
Inspect the brake switch, pedal stop and plunger for damage, wear or incorrect adjustment
Inspect the switch connector and wiring for corrosion, chafing, moisture or bent pins
Using live data, compare the brake switch A and B states with the pedal pressed and released
Check the relevant fuses and the supply voltage at the switch with the connector disconnected, following the wiring diagram for that model
Test the switch for correct operation and continuity in both pedal positions against the manufacturer's specification
Check the signal wire for short to voltage and for continuity back to the control unit

How to fix

Replace the brake switch if it is faulty or the contacts are stuck
Refit or adjust the switch and replace a worn or missing pedal stop or striker
Repair or replace damaged wiring and fix any short to voltage
Clean or replace corroded or damaged connectors and terminals
Replace blown fuses after finding and correcting the cause
Repair or replace the control unit only after the wiring and switch are proven good, and only if the manufacturer confirms it

Can I keep driving?

Medium severity

The car can usually be driven for a short time, but faulty brake light operation is a safety and legal issue, and cruise control or gearbox functions may be limited. Get it checked soon, and avoid driving if the brake lights do not work properly.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.