U0129Lost Communication With Brake System Control Module A
- Generic OBD-II code · Network
- Turns on the check-engine light
- Can trigger limp mode
- How the car detects it
- U0129 points to the brake system control module A, in GM vehicles the OBD node with diagnostic ID 7E5. GM's 2019 LTG engine table checks frames $0C1, $0C5, $0D1, $1C6 and others every 500 ms (one of them 10 s) and needs two trips to set the MIL; the 2018 hybrid controller and the 2025 ECM treat it as Type A, the 2017 table as Special Type C. Stellantis calls the partner Brake System Control Module 1. GM N192267870 adds a software case: after a jump start the 2019 Silverado ECM stored U0129 with U0101/U0140 and lit the service engine lamp. U0121 covers the ABS module, U0418 invalid brake data. Brake assist and stop-start may be reduced.
- What you may notice
- MIL or service engine lamp plus brake/ESC warnings
- Gear selection or stop-start blocked on some vehicles
- Several other U codes stored at the same time
- Likely causes
- LikelyFuse, supply or ground of the brake control module faulty
- PossibleLow battery or jump start leaving stored network codes (ECM update released)
- PossibleDamaged or corroded CAN wiring to the brake module
- RareBrake system control module internally faulty
- Repair
- Medium · 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.