P0703Brake Switch B Circuit
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Needs a drive cycle to confirm a fix
- How the car detects it
- Brake switch A is usually the brake light switch, B a second, redundant contact or signal used to cancel cruise control, release the converter clutch, check 'brake before throttle' and for stop-start. Since about 2014 GM receives it as a CAN message from the body module and checks its integrity (rolling counter, protection value: 3 of 10 faulty in 2014, 9 of 17 in 2025) without the check engine light; cruise control is disabled. Subaru-based systems (Saab 9-2X) check the circuit electrically during stops and starts and light the MIL after two trips. An NHTSA investigation of Hyundai and Kia brake light switches lists P0703 with a brake light that stays on. Brake switch A codes are P0571–P0573, disagreement between A and B is P0504.
- What you may notice
- Cruise control cannot be engaged or drops out
- Brake light stays on or does not work
- Selector cannot be moved out of P (shift lock)
- Check engine light depending on the maker
- Likely causes
- LikelyBrake light or double switch worn, corroded or misadjusted
- PossibleWiring or connector at the pedal damaged, fuse blown
- PossibleCAN message from the body module disturbed (GM: software, bus fault)
- RareAftermarket LED lamps or trailer module distorting the circuit
- Repair
- Easy · Often possible to do yourself.Typical cost: €20 – €150
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.