U04B5 code meaning
Invalid Data Received From Brake System Control Module B
What U04B5 means
Brake system control module B is a second brake controller. Bosch, for instance, adds a second, redundant brake unit to its Integrated Power Brake on automated vehicles so the car can still be stopped if the main unit fails, and the iBooster plus ESP pairing serves the same purpose. U04B5 is stored when a receiver gets messages from module B that fail plausibility, for example a wrong counter, checksum or pressure value. U0418 is the matching code for the primary brake module, U01B4 marks lost contact with module B and U031C a software mismatch. No manufacturer documents U04B5 publicly. As a safety system it rarely lights the MIL; expect brake or stability warnings, and driver assistance or automated functions may be switched off.
U04B5 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 3 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U04B5
- Brake, ABS or stability control warning
- Driver assistance or automated driving functions unavailable
Common causes of U04B5
- PossibleBrake control module B internally faulty
- PossibleChassis or private brake bus wiring or connector fault
- PossibleSoftware of the two brake modules not matching after update or replacement
- Less likelyWeak supply on the redundant power path
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Brake system module b
What each part of U04B5 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| B5 | The exact fault in that area. |
What to do next
- Note U04B5 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 U04B5
What does U04B5 mean?
U04B5 means "Invalid Data Received From Brake System Control Module B". Brake system control module B is a second brake controller. It is a generic code, so it means the same on every make.
Is it safe to drive with U04B5?
Drive gently and only to a workshop. With U04B5 the car can go into limp mode (reduced power) to protect itself.
Will U04B5 fail an emissions test?
U04B5 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 U04B5 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U04B5 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.