C05BA code meaning
Brake Booster Motor A Position Sensor Supply Circuit High
What C05BA means
C05BA covers the opposite case: the 5 V feed of motor A's position sensor rises above its upper limit. The usual culprit is a supply line touching a battery-voltage wire, less often a regulator that has lost control. No manufacturer publishes C05BA; GM's 2019 brake module treats its sensor supplies as high above 5.15 V for 100 ms, filing them under C05D1 or C05BB. TI's TPS7B4253-Q1 tracker shows how such outputs are protected: it survives a short to battery and opens its internal switch within about 1 ms. Hitachi Astemo deliberately places its supply monitor voltage at 3.75 V, below 5 V, so overvoltage stays measurable. An overvoltage can also damage the sensor, so assist is withdrawn and the booster runs without motor support.
C05BA at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of C05BA
- Brake warning lamp and assist warning message
- Hard brake pedal, longer stopping effort
Common causes of C05BA
- Most likelySupply line shorted to a battery-voltage circuit in the harness
- PossibleSensor supply regulator in the control unit no longer regulating
- Less likelyPoor control unit ground shifting the measured supply voltage
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Booster motor a pos sensor supplyElectric brake booster
What each part of C05BA means
| C | Chassis system: brakes, ABS, steering and suspension. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| BA | The exact fault in that area. |
What to do next
- Note C05BA 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 C05BA
What does C05BA mean?
C05BA means "Brake Booster Motor A Position Sensor Supply Circuit High". C05BA covers the opposite case: the 5 V feed of motor A's position sensor rises above its upper limit. It is a generic code, so it means the same on every make.
Is it safe to drive with C05BA?
Drive gently and only to a workshop. With C05BA the car can go into limp mode (reduced power) to protect itself.
Will C05BA fail an emissions test?
C05BA 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 C05BA to fix?
Difficulty: hard. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will C05BA clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.