Well, I had a thought how possibly turn off alarm on trailer disconnect - thus your scan was very welcome - thanks again!I'll leave you to pick the bones out of that
I had noticed there is coding difference between vans with factory installed towbar and vans without (or fitted with aftermarket one). Also a glimmer of hope was that the differing bits were not documented in VCDS nor in other tools.
The suspect coding: BCM byte 1: bit 2 and bit 6 were "11" without OEM towbar. With factory installed OEM towbar "00".
My van has a factory installed towbar and alarm - thus perfect testbed to try to disable OEM trailer alarm by tweaking those bits (to be the same as on yours).Here's what I did:
(1) Read BCM "blockmap" data, which contains
a) vans convenience system configuration: e.g. tailgate internal opening switch installed, function activated,...
b) switch, sensor, actuator, light, etc., statuses: e.g. window switch off, down, auto-down, etc.
Basically the data forms a matrix of 233 by 4.
Below a snippet how the decoded (by VCDS) matrix looks like.
(2) Changed the coding from "00" to "11"
(3) Read the blockmap data again
(4) Compared the blockmaps before and after to see if anything was changed by the coding - I was hoping to see e.g. an (undocumented) "installed" to be changed now to "not installed". Unfortunately, no change anywhere was detected - thus not was not expecting much further.
(5) Anyways, verified also on the van itself: plugged in the trailer, verified trailer was detected, lights were working, etc.
(6) Locked the van, waited 60 seconds, disconnected the trailer plug - alarm sounded. Thus no luck disabling OEM alarm for the trailer.
Conclusions?:
The (undocumented) coding difference between yours and mine doesn't disable trailer alarm. Actually couldn't spot the effect of the coding change. So remains a mystery why the codings are different from factory.
The tests above suggests that the trailer controller installed on yours doesn't have trailer alarm functionality.
Well, UNLESS someone can confirm the trailer alarm actually works also with aftermarket towbar controller - @Robert @Lukavell @JasonW @Van Buddy @rod_vw ??
Just another observation:
All the scans I have with the same aftermarket trailer controller have exactly the same coding - no help there either...
