Chassis, generic

C05C2 Brake Booster Motor A Over Temperature

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

The electric booster or integrated brake unit has found its drive motor A, or the power stage feeding it, too hot. GM uses the code in several EBCM tables, all Type A with MIL: one design trips above 154 °C estimated motor temperature or on a bridge driver over-temperature shutdown, the Cadillac XT4 unit above 120 °C and 142 °C rotor/ECU temperature, 23OBDG07 and 25OBDG03B also when torque limiting stops the plunger refill, and 25OBDG04B above 140/160 °C magnet or 210/240 °C winding temperature. Mitsubishi lists C05C2 for Outlander PHEV code C18E1-4B with MIL after two trips, although that page describes a missing supply to the stroke sensor. Expect reduced boost after long or repeated hard braking. C0594 covers motor performance.

Likely causes

Long downhill braking or repeated hard stops overheating the motor
Hydraulic fault making the motor run longer than normal
Power stage or bridge driver reporting false or real over-temperature
Low supply voltage forcing current limitation

Symptoms

  • Malfunction indicator lamp and brake warning on GM models
  • Reduced brake assist, pedal feels harder
  • Regenerative braking temporarily disabled

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time0.5–3 h

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

Parts involved

brake booster motor aelectric brake boosterbrake system control module

Related codes

C0594C0590C05B3C05C3

References: gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com, gsi.ext.gm.com.