C05B5 code meaning
Brake Booster Temperature Sensor C Circuit/Open
What C05B5 means
C05B5 is reserved for an interrupted circuit of booster temperature sensor C. No manufacturer documents it publicly; Mitsubishi, the one maker naming sensor C codes, reports problems with this channel only as C05B3 or C05B4. Boosters typically carry several NTC thermistors: Hitachi Astemo places one on the motor and one in the controller near the motor drive stage and caps motor current when either runs hot. If a thermistor or its lead breaks, the divider sits at one rail; a supplier overview cautions that such a rail reading alone cannot separate every wiring, reference or converter fault. Microchip adds that a board or module NTC follows case temperature, not the transistor junction. As the sensor is mostly internal, repair normally means a new booster unit.
C05B5 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyHard
- Typical labor1 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05B5
- Brake or brake system warning lamp on
- Booster may restrict assist as a precaution, depending on design
Common causes of C05B5
- Most likelyCracked thermistor body or broken lead inside the booster
- PossibleFractured solder joint on the control board from vibration or heat cycles
- Less likelyOpen wire or pin where the sensor is wired externally
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 C05B5 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B5 | The exact fault in that area. |
What to do next
- Note C05B5 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 C05B5
What does C05B5 mean?
C05B5 means "Brake Booster Temperature Sensor C Circuit/Open". C05B5 is reserved for an interrupted circuit of booster temperature sensor C. It is a generic code, so it means the same on every make.
Is it safe to drive with C05B5?
C05B5 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will C05B5 fail an emissions test?
C05B5 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 C05B5 to fix?
Difficulty: hard. A typical repair takes 1 to 3 hours of work. This is a job for a workshop.
Will C05B5 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.