Seat Mii Electric ABS and Traction Control Fault

That sounds remarkably similar to an issue I had with my Seat Ibiza. The ABS light and traction control problems are definitely concerning. Have you checked the input signal from the wheel speed sensors to the ECM? A faulty sensor or wiring could potentially cause this, and it might be worth investigating before assuming the entire control unit is defective. A diagnostic scan should point you in the right direction.

Thanks for the quick reply. When you say 'input signal from the wheel speed sensors to the ECM', are you referring to checking the wiring harness for continuity, or is there something more involved? And by diagnostic scan, do you mean using a standard OBD2 reader, or something more specialized?

Yes, I was referring to checking the wiring harness for continuity and proper voltage at the ECM connector. A standard OBD2 reader can give you some generic codes, but for ABS related issues, a scanner capable of reading manufacturer-specific codes is highly recommended. In my case, the initial scan pointed towards a wheel speed sensor issue, but further investigation revealed it was indeed a faulty ABS control unit. Given your symptoms, it's plausible that you have the same problem. I'd suggest getting a professional diagnostic performed to confirm the root cause before replacing any parts.

Just closing the loop on this speed signal fault. After a full diagnostic at the workshop, the control unit was indeed defective, as suspected. The repair set me back 1000€, a painful but necessary expense. Thanks for confirming my suspicions and suggesting I get it checked out professionally.