C05C9Brake Pressure Sensor Supply Circuit
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- Refers to the reference voltage the brake module provides to its hydraulic pressure sensors, not to one sensor's signal. If this feed collapses or rises, every sensor on it reads wrong at once, which is why the module checks the supply separately. Saab/GM monitors the 5 V reference of the brake pressure sensor and reacts within 0.1 s when that line touches ground or a voltage source. GM's integrated brake controller shows the usual window for such feeds: 4.85 to 5.15 V, held for 100 ms, on the pedal and motor sensor supplies (C05D1, C05BB). Tracking regulators like the TI TPS7B4253-Q1 are built for exactly this off-board sensor duty. No maker documents C05C9 itself. Unplug sensors one by one to find a shorted load.
- What you may notice
- Several brake pressure codes at the same time
- ABS, ESC and brake assist warnings, functions off
- Likely causes
- LikelyReference line shorted to ground or to battery voltage
- PossibleOne pressure sensor internally shorted, pulling down the shared feed
- RareSensor supply regulator inside the brake module defective
- Repair
- Medium · Usually a job for a workshop.Typical cost: €50 – €1,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.