I haven't bothered with the 3 small adjoining connectors as they aren't in use and I don't think related.

So.......

After exhausting all possibilities of incorrect wiring, shorts and bad earths I went out to my 4.8is and pulled the AHM module out if it. Before putting that module into the X5 that had the AHM burn out I popped the 2nd hand unit I bought into the 4.8is.

Immediately upon using any sort of lighting I had the "check trailer lights" message appear.

I then put the known good AHM module into my Diesel X5 and no more "check trailer lights" message.

So after about 25 hours of trouble shooting it turns out my soldering and rewiring job was perfect and the second hand AHM module I bought is faulty! :banghead::angryfire

UNBELIEVABLE! :rolleyes:

PS The reverse lights on the car are still supposed to light with a trailer on.:whistle:

Trailer control module issue
 

Good to have a second similar vehicle for part swap testing. (or in my case, bring a spare CPS to wife's X from mine to avoid calling a tow truck). Also happened once with fuel pump.

I would have already said new ≠ fixed, but i think you already mentioned the possibility. Good your sleuthing skills did get you there though!

You're at the point where i would say "piece of cake".

Ouch though.

Lol yep thanks.

With the faulty module half working and doing weird things it made the diagnosis a lot harder than if it flat out was dead.

Broken fully always better than intermittent! I've chased intermittent faults for months before finally replacing something.

Recently chasing faults on wife's car for over a month, misfires random cylinders, replaced plugs and coils it gets better then much worse and says error with intake air pressure.

Problem is with Valvetronic. No excuse the ECU didn't flag properly. The requested and actual angle not close but the errors were everything under the sun besides the actual problem.