C0589Brake Booster Motor A Position Sensor Circuit High
- Generic OBD-II code · Chassis
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- C0589 is the high counterpart: a sine or cosine line of motor A's position sensor reads above its permitted maximum. In GM's 2019 XT4 brake module a raw value above 2,795 counts, or a sum above 4,327, for 10 ms sets it; the 2023 and 2025 EBCM tables trip on a cosine reading above 4,075 counts lasting 0.15 s, a sine input above 2.252 V, or a calculated vector length above 1.14. GM classifies it as Type A, MIL on the first trip. Typical causes are a sensor line touching supply voltage or a broken sensor ground. Hitachi describes how a short to battery drives the evaluated signal to its upper limit, after which motor current is cut. Without a trustworthy rotor angle the booster cannot commutate its motor, so electric assist is withdrawn.
- What you may notice
- Brake assist warning with check engine lamp (GM)
- Hard pedal, assist withdrawn
- Likely causes
- LikelySensor signal line shorted to the sensor supply or battery voltage
- PossibleOpen sensor ground lifting the signals to the upper limit
- RareInternal sensor fault in the booster unit
- 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.