My FL 2 2011 HSE SD4 owned from new with 86k miles has developed the well known “Transmission Fault, traction reduced message” it happens every trip now and resets when ignition turned off.
We have replaced Haldex pump and propshaft ( which was well worn). Thoroughly checked the related wiring and nothing visible.
That did nothing to resolve the issue, changed the haldex ECU (second hand one) that didn’t help. Could be another dodgy ECU but……
This first happened shortly going over a lump of something on M62 at speed which took out O/S rear tyre. Again no visible damage but quite a coincidence.
Need some innovation as lack of diagnosis is getting expensive?
Have read ABS sensors can cause that error message.
Any thoughts welcomed.

I think you have answered your own question.

You need some diagnosis.

Either take it to a local indie garage, or main dealer if they are not going to charge a lot for diagnosis. Or get yourself a cheap F2 diagnostic tool, I got the Autel AP200, and do it yourself.

It will tell you exactly why the message is being displayed. May need some interpretation (eg cable rather than sensor) but it will tell you why the message is there.

Have you replaced the battery? A weak battery causes data line corruption when cranking over, giving that warning.