U015ALost Communication With Anti-Lock Brake System (ABS) Control Module B
- Generic OBD-II code · Network
- Can trigger limp mode
- How the car detects it
- U015A concerns a second anti-lock brake controller, module B. Vehicles prepared for automated driving need braking that still works after a single fault, so suppliers pair two independent units, for example Bosch's iBooster with the ESP control unit. If the partner that monitors module B, typically the primary brake controller or the driving automation computer, no longer receives its periodic messages, U015A is stored. No manufacturer documents this code publicly; the setting idea follows GM's generic rule for lost-communication codes (supervised message missing at 9-16 V). U0121 is ABS module A, U045B flags implausible data from B. Expect a brake or assistance warning and blocked automated functions.
- What you may notice
- Brake system or driver assistance warning in the cluster
- Automated driving or adaptive cruise functions unavailable
- Code stored in the primary brake controller
- Likely causes
- LikelyBrake module B without power or ground (own fuse in redundant layouts)
- PossibleBus line or connector to module B in the engine bay corroded or open
- RareBrake modules on incompatible software after repair
- RareABS control module B internally faulty
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €100 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.