Hello. I am now on my fourth Audi, and this time I have picked up an Audi A6 C6 3.0TDI quattro
The car itself is great, other than one engine mount that has to be replaced the car seems all fine and is truly a joy to drive.
I have on the other hand also had some issues with the car flashing the brake lights along with the ABS and ESP. This tends to stop after I either start the car off and on again, or I have to delete the fault codes manually.

The fault codes are listed below. It seems as if most of them are somehow connected (?)
I haven't really figured out how to fix it tho. Some posts say the ECU has to be recoded or something similar, and some say that the whole ABS control module has to be replaced.
I have found these (ABS control modules) to be quite expensive ... you can get them on ebay for a decent price tho, used that is.
If I have to change the ABS control module wouldn't that result in having to code it anyway?

Any ideas on what the issue could be? I will put the fault codes below, all help is appreciated!

P1647: «Check coding of ECUs in Data Bus powertrain».
P1653: «Please check DTC memory of: ABS ECU».
?: «Engine Control Module»
?: «Message for Delay Request».
U0401: «Invalid data from ECM/PCM -A-
P1881: «Data bus powertrain: missing message from acceleration request