OBD2 CODE

U1121 Communication network between control units (U)

We do not have a full sheet for this code yet, with its causes and checks. What you see here comes from the OBD2 code standard.

System: Communication network between control units (U)
Code type: Manufacturer-specific code: its exact meaning depends on the make.

What do I do now?

If the engine light flashes, the car loses a lot of power, overheats or the brakes fail, stop somewhere safe and call for assistance.
If the car drives normally, book a garage and show them this code: its exact meaning and the cause depend on each model.
Tell us what you notice: the diagnosis takes the code, your car and the symptoms into account.

This code does not point to the engine, the brakes or the transmission: you will see the X-ray car with no area marked.

Haldex 5 without communication or all-wheel driveDrivetrain / electronics

Engine / equipment: S1: Haldex 5 controller, reference 0AY907554F
Period mentioned: Only production periods and VINs documented in the application conditions.
Symptoms: Traction warning, absent AWD function and no communication.
Possible cause described: Controller failure confirmed through testing; no single internal mechanism published.
Check for the garage: Confirm reference; check pump, power and network before testing and repairing controller.
Cost cited in the source: No verified quote; confirm part and diagnosis.A rough figure from the original database, not an up-to-date quote.