Chassis, generic

C05B3 Brake Booster Temperature Sensor C Circuit Low

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

C05B3 means the third temperature channel of an electromechanical brake booster has dropped below its usable band. Mitsubishi documents the code for the Outlander PHEV: the DTC index pairs it with the brake unit's own code C18FC-18, EBA temperature sensor 1, and lights the brake system warning lamp plus the MIL after two trips. The value comes from the control electronics inside the electric intelligent brake unit. With the motor switch on, Mitsubishi stores the fault within one second if that reading is at or below −43 °C or at or above 169 °C. The fail-safe column says normal condition, so assist keeps working. Mitsubishi files its second sensor under C0579/C057A. Listed causes are harness, connector and the brake unit itself.

Likely causes

Fault in the temperature detection inside the electric brake unit's control module
Corroded or loose brake unit connector or damaged harness
Supply disturbance during start-up distorting the reading

Symptoms

  • Brake system warning lamp on
  • Check engine lamp on after two trips (Mitsubishi)
  • Braking assist usually unchanged

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 temp sensor celectric brake booster

Related codes

C05B4C05B5C05B6C05B7C0579

References: mitsubishitechinfo.com, mitsubishitechinfo.com, patents.google.com.