How to check if an A8 has servotronic, plus, where is the relay?

[Julian Thompson]

After a little more digging I found this table, attached, and the pic of inside one of these “relays” - it’s clearly the control module on the earlier cars, as it contains a lot of stuff which presumably later was moved to the valve on the rack.

Apparently the later servotronic module i have had the “boost” reduced in response to complaints from customers about too light steering, hence the earlier one was superceded.

That’s all on pre 2003 cars though, as per the table.

What I still can’t understand is why vcds can’t find the steering assist module on my car. Maybe I’m looking at the wrong module in vcds. I’ll have another look.

[MikkiJayne]

The valve on the D3 is still just a solenoid with no active trickery. The chip and circuitry in the D2 module is trivial to replicate in a body control module with a microcontroller though.

I don't think you'll find it as a discreet module in VCDS. It'll just be a sub-function of the body control module, and likely not even have anything to code or fiddle with, although it may throw a code if the solenoid is open circuit. The reduction in assistance will have been a software revision.

[Julian Thompson]

Agreed and thanks. So to summarise - d2 had the relay containing some processing. D3 did the processing in module J520 instead which connects directly to the valve on the rack.