C0637Brake Pressure Sensor G Circuit Low
- Generic OBD-II code · Chassis
- Can trigger limp mode
- How the car detects it
- C0637 reports that sensor G delivers less voltage than its lowest valid reading. Brake pressure sensors keep a live zero at rest, so a signal near 0 V means a fault rather than zero pressure: Saab's 9-5 ESP flags a pressure signal under 0.25 V lasting 0.1 s, and GM's 2016 hybrid brake module treats under 0.3 V for 0.1 s on its left rear wheel pressure sensor (sensor D there) as a short to ground, Type A. Common causes are a signal wire chafed through to the body, a 5 V reference pulled down, or a failed sensor. Which component G is stays open; in a seven-sensor unit like the Lucas/ZF design it would be one of the wheel, supply or push-through sensors. G usually sits in the hydraulic block, so a sensor defect often means replacing that block.
- What you may notice
- ABS and ESC warning lamps on
- Live data shows no pressure even when the pedal is pressed
- Likely causes
- LikelySignal wire chafed and shorted to ground
- Possible5 V sensor reference shorted to ground or interrupted
- PossibleSensor G defective, often only replaceable with the hydraulic unit
- Repair
- Hard · Usually a job for a workshop.Typical cost: €60 – €1,800
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.