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!

Chassis generic / SAE

P25C4

Brake Booster Temperature Sensor A Circuit

The temperature sensor monitoring the electric brake booster (iBooster, eBooster) returns no usable signal. Without temperature feedback the controller derates booster assist to protect the motor.

SystemChassis
Typegeneric / SAE
GroupP2
Range / number5 / C4

Possible causes

  • Open sensor element or broken sensor wire high
  • Corroded connector on the booster sensor pigtail medium

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: hard
  • DIY: shop recommended
  • Estimated cost: 200–1500 €
  • Estimated time: 1–4 h
  • Component: electric brake booster
  • Component: temperature sensor
  • 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