Trailer control module issue

[Homerlovesbeer]

Hi all,

The X5 I bought had someone do a dodgy wiring for a reverse camera where they didn't go through the rear tailgate grommet so water ended up in the battery tray and the Trailer Control Module caught fire and melted the connector.

I cut off the burnt connector and bought another TCM plus connector and painfully soldered all the wires together.

After connecting the TCM and turning the car on I get the dreaded fast indicators after a few seconds and then the "check trailer lights" error message.

I've painfully traced all wires and they have continuity and are in the correct wiring order.

With the TCM module NOT installed my lights work normally.

Something I've noticed is if the TCM is installed, all the lights work on the car EXCEPT the reverse lights. I have not hooked up a trailer however I have tested all the trailer coupling pins and all are powering on as they should. Even the reverse pin for the trailer receives a 12V signal with the car in reverse.


If I disconnect the TCM module the reverse lights on the car now work as normal.

I really have no idea what's going on. It's like the Light Control Module stops sending a reverse signal to the car lights with the TCM connected yet is happy when it isn't connected?

I've confirmed that no power is being sent to the car reverse lights with the TCM installed.

Ideas? I'm running out of them and spent days diagnosing using wiring diagrams from ISTA.

EDIT: Chatgpt reckons the module needs coding to the car even though it's itentical with the same part number as the old burnt out item?