C05D5 code meaning
Brake Master Cylinder Cut Off Valve
Chassis system Generic code C05xx codes Check engine light
What C05D5 means
Electrical fault of the solenoid valve that separates the master cylinder from the wheel circuits in by-wire operation, so pressure comes from the motor and the pedal works against a simulator. In GM's booster-type EBCMs (XT4, 23OBDG07, 25OBDG03B) the valve driver reports over-current of about 4 to 6.5 A, an output stage above 195-220 °C, a lost power ground or lost freewheeling within 0.03 s. GM's integrated controller maps open and shorted driver tests of its simulator-side valve to C05D5 (Type A, MIL) but a coil above 265 °C as Type C without MIL; 25OBDG04A uses it for the traction control isolation valves. Bosch describes these isolation valves closing during by-wire braking. Expect reduced assist or a mechanical push-through fallback.
C05D5 at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05D5
- Malfunction indicator lamp and brake warning
- Loss of brake assist, pedal works on the master cylinder directly
- ESC and traction control limited
Common causes of C05D5
- Most likelyValve coil shorted or open inside the hydraulic unit
- PossibleValve driver stage or ASIC in the module defective
- PossiblePoor power ground of the brake module
- Less likelyValve overheated by excessive activation time
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Master cylinder cutoff valveBrake system control module
What each part of C05D5 means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| D5 | The exact fault in that area. |
What to do next
- Note C05D5 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 C05D5
What does C05D5 mean?
C05D5 means "Brake Master Cylinder Cut Off Valve". Electrical fault of the solenoid valve that separates the master cylinder from the wheel circuits in by-wire operation, so pressure comes from the motor and the pedal works against a simulator. It is a generic code, so it means the same on every make.
Is it safe to drive with C05D5?
Drive gently and only to a workshop. With C05D5 the car can go into limp mode (reduced power) to protect itself.
Will C05D5 fail an emissions test?
C05D5 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 C05D5 to fix?
Difficulty: workshop only. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will C05D5 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.