U015A code meaning
Lost Communication With Anti-Lock Brake System (ABS) Control Module B
What U015A means
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.
U015A at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U015A
- Brake system or driver assistance warning in the cluster
- Automated driving or adaptive cruise functions unavailable
- Code stored in the primary brake controller
Common causes of U015A
- Most 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
- Less likelyBrake modules on incompatible software after repair
- Less likelyABS control module B internally faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ABS module bCAN bus
What each part of U015A means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5A | The exact fault in that area. |
What to do next
- Note U015A 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 U015A
What does U015A mean?
U015A means "Lost Communication With Anti-Lock Brake System (ABS) Control Module B". U015A concerns a second anti-lock brake controller, module B. It is a generic code, so it means the same on every make.
Is it safe to drive with U015A?
Drive gently and only to a workshop. With U015A the car can go into limp mode (reduced power) to protect itself.
Will U015A fail an emissions test?
U015A is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U015A to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will U015A clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.