P0703 Code: Brake Switch B Circuit — Causes & Fix
P0703 means a fault in the brake switch "B" circuit — a brake-signal input used by the transmission/torque-converter and cruise control.
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $20 – $250
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include a failed/misadjusted brake switch, a blown fuse, or wiring faults. P0703 is a generic OBD-II code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer OBD-II vehicle regardless of make. Fix the underlying fault, then clear the code with an OBD-II scan tool — it will return if the problem isn't resolved.
Symptoms
- Check engine light on
- Torque-converter clutch or cruise issues
- Brake lights or shift-lock quirks
How to fix it
- 1
Check the brake switch
1. Confirm the brake lights work and the switch is adjusted correctly. 2. Replace a faulty switch.
- 2
Inspect wiring/fuse
1. Check the switch connector and fuse. 2. Repair, then clear the code.
Frequently asked questions
Why does P0703 affect the transmission?
The transmission uses the brake signal (e.g. to release the torque-converter clutch). A faulty brake switch can cause shift/converter quirks.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.