Chassis, generic

C05B4 Brake Booster Temperature Sensor C Circuit High

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

C05B4 is the upper-limit counterpart: temperature channel C of the electric booster reports a value above its permitted maximum. In Mitsubishi's Outlander PHEV index it stands next to C18FC-19, again EBA temperature sensor 1, with the same lamp logic – brake system warning lamp and MIL after the second trip. Mitsubishi's description page for this subcode repeats the criteria of C05B3 word for word (−43 °C or colder, 169 °C or hotter, detected within one second), so the split into low and high lies in the electrical evaluation, not in the published temperatures. Whether a high signal stands for heat or cold depends on how the thermistor is wired in its divider. Because the sensor sits on the control board, a persistent fault usually means replacing the brake unit.

Likely causes

Temperature circuit on the brake unit's control board defective
Poor contact at the brake unit connector or chafed wiring
Genuinely excessive electronics temperature after heavy booster use

Symptoms

  • Brake system warning lamp on
  • MIL on after the second trip (Mitsubishi)
  • Code returns immediately after clearing if the unit is defective

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

C05B3C05B5C05B6C05B7C057A

References: mitsubishitechinfo.com, mitsubishitechinfo.com, passive-components.eu.