Quote Originally Posted by Dan_3MPS View Post
01299, 01336 and 00457 as you've listed above are CAN communication errors, which if you cut wires to splice may have happened then or are an indication your soldering isn't holding a reliable connection on one or both the wire pairs.

01044 will go away once you tell the gateway a trailer module is installed.

Edit - based on my experience with a MK6 Golf install, but I used VCDS so can't help you with the OBD11 tool coding.
I cleared the trouble codes and had a drive and rescanned for faults.

The only remaining one was the trailer module not coded.

I am pretty sure my soldering is good. I suspect that it might be a case that the CAN-bus has something of a backup capacitor or can detect shorts or open circuits when the power is lost so during the cutting and splicing there would have been open and short circuits that might have been detected even with the battery disconnected.
Anyway, they have been cleared and didn't come back during the short drive which was the same as the test drive I did after splicing the wires.

Someone will know what Byte the trailer bit is on and which bit.. from my reading it looks like Byte 3 bit 6.

Cheers,
Chris