C0588Brake Booster Motor A Position Sensor Circuit Low
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- C0588 is set when the position signal of booster motor A sits below its valid band. GM documents it in its EBCM tables: the 2019 Cadillac XT4 unit trips when a raw sine or cosine value drops under 1,300 counts, or their sum under 3,876, for 10 ms; the 2023 and 2025 tables use a cosine value under 10 counts for 0.15 s, a sine line under 1.047 V or a vector length below 0.25. GM rates every variant Type A, lighting the MIL on the first trip. A low value points to a grounded signal line or missing sensor supply; Hitachi's resolver patent notes that a ground short pulls the output to 0 V. Infineon's TLE5009, a sine/cosine angle sensor intended for motor commutation, specifies a valid vector band for the same reason. Assist is cut or limited, and often the booster unit must be replaced.
- What you may notice
- Check engine lamp together with brake/ABS warning (GM)
- Electric assist switched off, high pedal effort
- Likely causes
- LikelySine or cosine line of the sensor shorted to ground
- PossibleMissing sensor supply, signals collapse toward zero
- RareSensor element or target magnet damaged, amplitude too small
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €2,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.