Trailer Wiring

[TDI_Guy]

Was out at my storage compound getting my boat ready for the season. Thought I'd better test the trailer wiring - good thing I did, I have a problem...

- Turn signals - work fine
- Marker lights (headlights on) - work fine
- Brake lights - do not function. Interesting - the MFI indicates there is a trailer brake light problem.

All worked fine with my X5. I got my brother to hook up his navigator just as a check - and trailer works fine.

It seems that I have a problem with either the VAG coding (seems unlikely given that MFI noted a problem), the trailer control module - or last possibility - the 7 to 4 pin adapter. I noticed today that my adapter (which is a Pollak) - which came from my X5) has two locations with no connections - I am wondering if it is possible that the Treg needs a particular type of 7 to 4 adapter?

Anyone have any specific knowledge on this?

[TDI_Guy]

The Search function is a wonderful thing... Tried a few new combinations and came up with what looks to be the answer (from 2005):

"The second issue , which is the same one I experienced and is the one that concerns you, occurs because the modules are coded to European standards... which uses a separate wire for the brake lights. We control our brake lights via the turn signal lights. This is the prior post that explains that:

"Using the hitch recepticle, I have no brake lights. Maybe the installer missed this instruction - "Using the VAG 5051 tool: Go to address 69 (trailer function). Go to 07 (control unit). Press 2 to reprogram modul for brake light function."

You can do the same thing yourself (I did) with a VagCom. Reprogram address 69 (trailer function) from the value of "1" to the value of "2" and you will enable your brake lights and your surge brakes."

Is there any good reason that the factory in their infinite wisdom would not set the programming to enable the brake lights???