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

P0556

Brake Booster Pressure Sensor Circuit Range or Performance

Same as P0555 with the signal in plausible range yet not matching the engine model - drift, partial blockage of the reference port.

SystemPowertrain
Typegeneric / SAE
GroupP0
Range / number5 / 56

Possible causes

  • Sensor element drifted high

Symptoms

  • Check engine light on
  • Significant power loss / limp mode
  • Possible blue or black smoke from exhaust
  • Whistling or hissing sound from intake

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 80–320 €
  • Estimated time: 0.4–1.4 h
  • Component: brake booster pressure sensor
  • 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