U031C code meaning
Software Incompatibility With Brake System Control Module B
Network system Generic code U03xx codes Check engine light
What U031C means
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.
U031C at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U031C
- 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
Common causes of U031C
- Most likelyBrake booster unit replaced or swapped without programming to the vehicle
- PossibleStability control module updated or configured for another booster variant
- Less likelyProgramming interrupted, for example by low battery voltage
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake system module bControl module software
What each part of U031C means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 1C | The exact fault in that area. |
What to do next
- Note U031C and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U031C
What does U031C mean?
U031C means "Software Incompatibility With Brake System Control Module B". 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. It is a generic code, so it means the same on every make.
Is it safe to drive with U031C?
Drive gently and only to a workshop. With U031C the car can go into limp mode (reduced power) to protect itself.
Will U031C fail an emissions test?
Yes, it can. U031C is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U031C to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U031C clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.