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

P256B

Engine Idle Speed Selector Sensor/Switch Range/Performance

The idle-speed selector input is electrically intact but the value does not match a valid preset — multiple positions or a non-mappable value. Often a sticky multi-position switch.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 6B

Possible causes

  • Contaminated rotary contact high
  • Sensor element aged beyond calibration window low
  • Sensor mounting loose - signal damping low

Symptoms

  • Check engine light on
  • Idle speed too high, too low, or unstable
  • Possible stalling at idle or after cold start

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 60–350 €
  • Estimated time: 0.3–1.5 h
  • Component: idle speed selector switch
  • 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