Diagnostic trouble code P0703 — what it means, the common
causes, and how to confirm the real fault before replacing parts.
What does P0703 mean?
P0703 indicates: Brake Switch 'B' Circuit.
This relates to the Transmission system.
Common causes of P0703
brake light switch signal failure
failure of Hall element in brake light switch F on tandem master cylinder
What to check (live data)
brake switch signal on powertrain CAN data bus ('brake pressed' signal present/absent)
Parts often involved in P0703
brake light switch F
tandem master cylinder
Don't replace parts until the root cause is confirmed — many of these codes are caused by wiring, a connector or an upstream fault, not the part itself.
Get the confirmed root cause for P0703 — on YOUR vehicle
A code is a symptom, not a diagnosis. AutoDX Pro cross-checks several
independent assessments, pinpoints the actual root cause, gives you the
exact tests to confirm it, and shows the parts — only after the cause is
confirmed. Reads your scan-tool photo and decodes your VIN with open
recalls.
P0703 is a diagnostic trouble code: Brake Switch 'B' Circuit.
What are the common causes of P0703?
Common causes include: brake light switch signal failure, failure of Hall element in brake light switch F on tandem master cylinder. The exact cause depends on the vehicle — confirm it before replacing parts.
Can I keep driving with P0703?
It depends on the fault and your symptoms. Some causes are minor, others can damage components or affect safety. Get the root cause confirmed before deciding.
How do I fix P0703?
Confirm the actual root cause with targeted tests first, then replace only the part that's at fault. AutoDX Pro gives you the root cause, the exact tests, and the parts for P0703 on your specific vehicle.