C05B4 code meaning
Brake Booster Temperature Sensor C Circuit High
Chassis system Generic code C05xx codes Check engine light
What C05B4 means
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.
C05B4 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05B4
- Brake system warning lamp on
- MIL on after the second trip (Mitsubishi)
- Code returns immediately after clearing if the unit is defective
Common causes of C05B4
- Most likelyTemperature circuit on the brake unit's control board defective
- PossiblePoor contact at the brake unit connector or chafed wiring
- Less likelyGenuinely excessive electronics temperature after heavy booster use
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake booster temp sensor cElectric brake booster
What each part of C05B4 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B4 | The exact fault in that area. |
What to do next
- Note C05B4 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about C05B4
What does C05B4 mean?
C05B4 means "Brake Booster Temperature Sensor C Circuit High". C05B4 is the upper-limit counterpart: temperature channel C of the electric booster reports a value above its permitted maximum. It is a generic code, so it means the same on every make.
Is it safe to drive with C05B4?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will C05B4 fail an emissions test?
C05B4 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is C05B4 to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will C05B4 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.