OBD-II code · Network
U0129 Lost Communication with Brake System Control Module
The Brake System Control Module has stopped transmitting on the vehicle data bus, so other control units no longer receive its messages. ABS and electronic brake functions are lost; base braking remains but the assists are off. Typical causes are loss of power or ground at the module, an open or shorted CAN/LIN bus wire, a connector fault, or an internal module failure.
Is it safe to drive with U0129?
The car may go into limp mode (reduced power). Get it diagnosed before a long trip.
Common causes
- Most likelyBrake module unpowered
- PossibleCAN wiring to brake module broken
- Less likelyGateway module routing CAN messages incorrectly
Symptoms
- Multiple warning lights may illuminate
- Affected modules may go into limp mode or shut down
- Specific functions inoperative depending on module
- Diagnostic tools may show communication faults
Repair at a glance
- Difficulty
- Hard
- DIY friendly
- Best left to a mechanic
- Typical labour
- 1–6 h
- Emissions test
- Usually unaffected
- Parts involved
- Brake System Control Module, Can Bus Wiring
Related codes
- U0126Lost Communication with Steering Angle Sensor Module
- U0127Lost Communication with Tire Pressure Monitor Module
- U0128Lost Communication with Park Brake Control Module
- U012ALost Communication With Chassis Control Module A
- U012BLost Communication With Chassis Control Module B
- U012CLost Communication With Active Vibration Control Module
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.