Garage computer connection not working

[duggo]

Hi all,

Recently a yellow ABS warning light has come on in my 98 A4 1.8L petrol.
To reset this I asked the garage to connect it to the computer to reset this light. But the garage computer cannot connect to the car's computer!!
I've tried two garages the second tells me it the computer is able to connect 99% of the time but its just unfortunate your that 1%. They then said they would need more time to solve this issue.
I have not had time to bring it back to the garage and i don't intend to buy VAG-Com hardware and software if it will not work.

Has anyone heard of this issue before?
I assume its a fault with the cable going to the cars computer have you any thoughts?

Thanks

[Theresias]

Sounds like the typical aftermarket radio problem...

http://www.ross-tech.com/vag-com/aftermarket-radio.html

[Uwe@Ross-Tech]

Could also be a failed ABS controller. ABS controllers from that vintage A4, A6, and Passat (roughly 1998-2001) are somewhat notorious for failing in a manner where the do not communicate and sometimes block communications with other modules as well.

So the question is, can the Garages' computers connect to other modules in the car (for example the engine) or can they not connect to anything at all?

Another thing that can block all connections in that vintage of Audi is a radio which has no power at all (for example due to a blown fuse).

If they cannot connect with anything at all, and the factory radio is still there (and works), then I would try disconnecting the ABS controller from the car's harness. If they can then communicate with other modules, you'll need a new ABS controller.

-Uwe-