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.

Real-world scan data

Seen in

362

scans in the past year

Found in

0.1%

of scans

0.1%

of scans that found faults

Appears alongside · share of P0703 scans

P0571in 30.9% of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

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.

Read & clear P0703 yourself

Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.

▶ Get it on Google Play

✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX