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

P25B7

Auxiliary Ignition Switch On/Start Position Circuit

General electrical fault on the auxiliary ignition switch On/Start input. Used on commercial vehicles or upfit applications where a second ignition switch (in a sleeper cab, work platform or crew compartment) can crank the engine.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / B7

Possible causes

  • Open or shorted wire high

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 80–500 €
  • Estimated time: 0.5–2 h
  • Component: auxiliary ignition switch
  • Component: wiring harness
  • 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