Powertrain, generic (extended)

P25C4 Brake Booster Temperature Sensor A Circuit

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

P25C4 covers the first temperature sensor of an electromechanical brake booster, in which an electric motor and gear set take the place of the vacuum diaphragm, as in Bosch's iBooster. The booster electronics use this value to protect motor and control unit from overheating during long or repeated braking. P25C4 reports an unusable sensor circuit without a direction. GM's 2023 Corvette Z06 table 23OBDG07 lists only the separate low and high codes P25C6 and P25C7 for this sensor in its EBCM section, plus C0579 and C057A for a second sensor; a generic circuit code does not appear there, and no manufacturer publishes P25C4. GM requires the booster temperature sensors to be fault free before it runs its rotor and ECU over-temperature checks, so a failed sensor removes that protection.

Likely causes

Temperature sensor inside the booster unit defective
Corroded or loose booster connector
Fault in the booster control electronics

Symptoms

  • Brake system warning in the cluster
  • Brake pedal may feel harder if assistance is reduced
  • Stored code, often together with chassis codes

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€150–2,500
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

electric brake boostertemperature sensorwiring harness

Related codes

P25C5P25C6P25C7P25C8C057B

References: gsi.ext.gm.com, bosch-mobility.com.