OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

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.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number7 / 03

Possible causes

  • Open in switch or wiring high

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

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 60–250 €
  • Estimated time: 0.3–1.2 h
  • Component: brake switch b
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication