U031CSoftware Incompatibility With Brake System Control Module B
- Generic OBD-II code · Network
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- In GM's hybrid OBD tables brake system control module B is the electromechanical brake booster (Bosch iBooster), which builds brake pressure without engine vacuum and works hand in hand with the stability control unit. The 2016 to 2019 tables describe the check behind U031C: the stability module receives a compatibility index from the booster over CAN and compares it with its own configuration. If the index stays incompatible for 0.1 s, the code is stored, provided supply voltage is between 7.5 and 16 V, the bus is active and 5 s have passed after a power mode change. GM classes it as Type A: the warning lamp comes on during the very first drive with the fault. U01B4 is lost contact, U04B5 invalid data from module B, U0318 concerns the main brake module. Expect brake warnings and possibly reduced electric boost.
- What you may notice
- MIL on and brake or stability warning in the cluster
- Changed pedal feel or reduced electric brake boost
- Code appears right after brake booster or ESP module work
- Likely causes
- LikelyBrake booster unit replaced or swapped without programming to the vehicle
- PossibleStability control module updated or configured for another booster variant
- RareProgramming interrupted, for example by low battery voltage
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €80 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.