C05CA code meaning
Brake Master Cylinder Piston Position Sensor A Circuit Voltage High
Chassis system Generic code C05xx codes Check engine light
What C05CA means
Channel A of the travel sensor at the master cylinder input rod reports a signal beyond its upper limit. In GM's booster-type brake modules this channel is a linear position sensor (LiPS) that talks to the EBCM digitally over SENT, so the high error is a message from the sensor itself: the Cadillac XT4 table in 19OBDG03D reacts within 0.033 s on the fast channel, 23OBDG07 and 25OBDG03B after 0.96 s on the slow channel, Type A with MIL. Line shorts and lost messages are filed under separate network codes there. Continental describes pedal modules that read travel with two sensors so one bad channel can be identified. Check the sensor connector and supply before replacing the booster assembly. C05CB is the low counterpart.
C05CA at a glance
- Check engine lightYes, usually on
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05CA
- Malfunction indicator lamp plus brake warning on GM models
- Reduced brake assist or changed pedal feel
Common causes of C05CA
- Most likelyPosition sensor A reporting out-of-range high internally
- PossibleSupply voltage of the sensor out of tolerance
- Less likelySensor magnet or input rod out of position
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Master cylinder pos sensor aElectric brake booster
What each part of C05CA means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| CA | The exact fault in that area. |
What to do next
- Note C05CA 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 C05CA
What does C05CA mean?
C05CA means "Brake Master Cylinder Piston Position Sensor A Circuit Voltage High". Channel A of the travel sensor at the master cylinder input rod reports a signal beyond its upper limit. It is a generic code, so it means the same on every make.
Is it safe to drive with C05CA?
Drive gently and only to a workshop. With C05CA the car can go into limp mode (reduced power) to protect itself.
Will C05CA fail an emissions test?
C05CA 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 C05CA to fix?
Difficulty: hard. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will C05CA clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.