U04BB code meaning
Invalid Data Received From Switch Input Module B
What U04BB means
U04BB concerns the second switch input module. A receiving controller still hears module B on the bus, but the switch information inside its frames fails the plausibility, counter or checksum test. Where buttons are split across several housings, a modular layout like the one in a BCS Automotive Interface Solutions patent is typical: a main module identifies each attached satellite by a coded type and translates its signals for the CAN or LIN bus. A satellite reported with the wrong type or a coding mismatch after a part swap can produce exactly this kind of unusable data. No carmaker publishes a text for U04BB. U01B8 stands for total silence of module B. Expect individual buttons, often a group in one console or panel, to stop responding.
U04BB at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U04BB
- A group of buttons in one panel not responding
- Functions switching on by themselves or not switching off
Common causes of U04BB
- Most likelyReplacement switch module of the wrong variant or not coded to the vehicle
- PossibleSwitch input module B internally faulty
- Less likelyLoose or corroded plug between satellite and main module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Switch input module b
What each part of U04BB means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| BB | The exact fault in that area. |
What to do next
- Note U04BB 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 U04BB
What does U04BB mean?
U04BB means "Invalid Data Received From Switch Input Module B". U04BB concerns the second switch input module. It is a generic code, so it means the same on every make.
Is it safe to drive with U04BB?
U04BB does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will U04BB fail an emissions test?
U04BB 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 U04BB to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. This is a job for a workshop.
Will U04BB clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.