P0703
Brake Switch B Circuit
A general circuit fault on the secondary brake switch B - typically used as redundant input for safety-critical functions like cruise control cancellation and shift-interlock.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: easy
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
Common causes
Ordered by how often each turns out to be the cause.
- Open in switch or wiringCommon
Parts involved
- Brake Switch B
P0703 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.