P0703
Brake Switch B Circuit
Transmission / brake switch input
Generic OBD-II
High
What it means
P0703 means the powertrain or transmission computer sees a fault in the brake switch "B" input signal. The transmission uses the brake signal to unlock the torque converter and to allow shifting out of park, and it is shared with cruise control. Your brakes themselves are not affected, but a faulty or misadjusted brake switch can cause surging, cruise-control dropouts, and shift-interlock issues.
High
Can I keep driving? Drivable — your brakes work normally, but cruise control, torque-converter lockup, or the shift interlock may misbehave until the brake switch is fixed.
Common symptoms
What you'll notice
- Check-engine light on
- Cruise control will not engage or drops out
- Erratic or no torque-converter lockup, causing surging
- Trouble shifting out of park (shift interlock affected)
Common causes
Most likely first
- Faulty or misadjusted brake light switchLikely
- Blown brake-light fuse or shorted brake switch wiringCommon
- Corroded or loose connector at the brake switchCommon
- Wiring fault, or less often a TCM/ECM input faultLess often
How to diagnose & fix
Work through it in order
- Check that the brake lights work correctly, since the same switch feeds this circuit.
- Inspect and, if needed, adjust the brake pedal switch to spec.
- Test the switch wiring and connector for opens, shorts, and the correct signal when the pedal is pressed.
- Replace the brake switch if it fails testing, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P0703?+
Your brakes still work, so it is generally safe, but cruise control and smooth shifting may be affected until it is repaired.
Can I just clear P0703?+
It will return unless the brake switch or its wiring is repaired or adjusted.
Related codes
Often seen with P0703
Read & clear P0703 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX