OBD-II Code P0703 — What It Means & How to Fix It

What Does This Error Mean?

P0703 means the brake pedal switch input to the Transmission Control Module is faulty — the TCM cannot reliably tell whether the brake pedal is pressed. This matters because the TCM uses brake input for shift-lock release and torque converter clutch disengagement. The brake light may stay on, may not work at all, or the shifter may refuse to leave Park.

Affected Models

All vehicles 1996+ with brake-shift interlock
Very common in older GM trucks (Silverado, Sierra)
Common in Ford F-150 and Explorer
Common in Honda Civic and Accord

Common Causes

Failed brake pedal switch (most common cause)
Brake switch out of adjustment so the plunger is not contacted correctly
Wiring fault or open circuit between brake switch and TCM
Blown brake light fuse
Faulty TCM input pin (uncommon)

How to Fix It

Check whether the brake lights work.

Have someone press the brake pedal while you watch the rear lights. No brake lights confirms a switch or fuse issue — this is the easiest first check.
Check the brake light fuse.

Find the fuse for STOP LAMP or BRAKE in the fuse panel. A blown fuse is the cheapest fix — replace and retest before deeper diagnosis.
Inspect the brake pedal switch.

The switch is mounted on the pedal arm. Check that the plunger is being depressed correctly when you release the brake. A misaligned switch causes intermittent P0703.
Replace the brake switch if other tests fail.

Most modern brake switches are quarter-turn or clip-in — a 10-minute job. Order the correct part for your vehicle from a parts store or online.
Test wiring continuity if a new switch does not fix it.

Use a multimeter to test continuity from the brake switch connector to the TCM pin. An open circuit means damaged wiring that needs repair.

When to Call a Professional

Brake switch replacement is straightforward DIY for most vehicles — the switch sits on or near the brake pedal arm and clips in. A shop charges USD 80–180 for the job. Switches themselves are USD 15–50. If wiring tests bad, professional electrical diagnosis runs USD 100–200.

Frequently Asked Questions

Can I drive with P0703?

Yes, but with caution. The shift-lock interlock may not work, meaning the shifter may move out of Park without depressing the brake — a safety hazard around children. Fix promptly.

Why does the shifter not come out of Park with P0703?

The shifter interlock requires a confirmed brake pedal press to release Park. If the TCM cannot read the brake switch, the interlock stays engaged. Most vehicles have an emergency override slot near the shifter — refer to the owner's manual.