C05BABrake Booster Motor A Position Sensor Supply Circuit High
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- 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 An overvoltage can also damage the sensor, so assist is withdrawn and the booster runs without motor support.
- What you may notice
- Brake warning lamp and assist warning message
- Hard brake pedal, longer stopping effort
- Likely causes
- LikelySupply line shorted to a battery-voltage circuit in the harness
- PossibleSensor supply regulator in the control unit no longer regulating
- RarePoor control unit ground shifting the measured supply voltage
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €3,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.