U045B code meaning
Invalid Data Received From Anti-Lock Brake System (ABS) Control Module B
What U045B means
ABS module B is a second brake controller, found where braking has to survive a single fault. Bosch pairs an electromechanical booster or its integrated power brake with ESP for that purpose and, for automated driving, adds a separate redundant brake unit; its 2018 show message was that automated driving needs redundancy. U045B is stored when the partner, often the main brake unit or the automated driving computer, receives status or wheel data from B but rejects them because counters, checksums or values do not fit; U015A means B is silent, U0415 concerns the main ABS module. No manufacturer documents U045B publicly. Normal braking usually remains through the other path, yet a brake warning may appear and anything that relies on redundancy, such as automated or hands-off driving, is blocked.
U045B 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 U045B
- Brake system or ABS warning
- Automated or hands-off driving functions unavailable
Common causes of U045B
- Most likelySoftware levels of brake module A and B or the automation computer not matching
- PossibleWeak supply or ground of brake module B
- Less likelyInternal fault of brake module B
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
ABS module b
What each part of U045B means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 5B | The exact fault in that area. |
What to do next
- Note U045B 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 U045B
What does U045B mean?
U045B means "Invalid Data Received From Anti-Lock Brake System (ABS) Control Module B". ABS module B is a second brake controller, found where braking has to survive a single fault. It is a generic code, so it means the same on every make.
Is it safe to drive with U045B?
Drive gently and only to a workshop. With U045B the car can go into limp mode (reduced power) to protect itself.
Will U045B fail an emissions test?
U045B 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 U045B to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 3 hours of work. This is a job for a workshop.
Will U045B clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.