A4 Avant Towbar Electrics Problem

[D4nvant]

Hi all, hoping you can help.
I have fitted a PF Jones 13 pin wiring kit to my A4, (no red towing plug in boot, so had to solder into CAN system and brake light signal to fit plug for trailer module) I followed the instructions to a tee and thought I had done a cracking job.

Problem is, my brake lights are now stuck on permanently with ignition and engine on. I have checked my wiring and definitely all in the correct place, with two can wires soldered into and also the brake signal.
My thought is that the problem lies with the brake signal wire giving me a 50026 ‘brake light switch- signal implausible’ fault.
Instructions said to wire in to the RED/BLACK wire.
Being an LED brake light assembly and also a LED friendly trailer module, I am wandering if the brake lamp signal is actually needed?

I have tried running VCDS with the trailer plug disconnected and was presented by multiple trailer module not detected faults, so I know it’s coded up correctly. Also checking with trailer light tester, all lamps are functioning (just brake lights stuck on all the time) (indicators, fogs, reverse and hazards all work as intended)

I have trawled the forums and have discovered that in some cases with PF Jones wiring kits, the RED/BLACK wire on the VAG kits is sometimes not required after a certain model year, however this is not specified in the instructions for the A4.
I am going to give PF Jones a call tomorrow to see what they say, and I suppose I may be answering my own question, but the next step is to check functionality is restored after disconnecting the join on the BLACK/RED wire I’ve tapped into?
Thanks,
Dan

 

[D4nvant]

Thread update for future users.

Tried swapping the Red/Black feed to the Black/Red connected to BCM in boot with no avail, which is also what PF Jones suggested over the phone,

performed a brake switch test using VCDS and confirmed that brake switch was working by viewing live data.
Removed everything related to the towing system from car including CANBUS wires that were soldered in, de-configured all modules to do with towing and cleared all codes, fault persisted with brake lights stuck on.

checked voltage on 32Pin plug into BCM while brake pedal depressed on Red/Black wire, no voltage.

Cause was a break in the wire about 10mm behind solder connection. Removed break and re soldered, problem fixed.
Re fitted towing electrics and re-coded using VCDS, all now operational.

Hope no one else has this headache, but be careful when stripping the wire into BCM, as they are quite delicate and it would appear my wire strippers were a little overkill!
Good luck!