[5potnoodle]

Hi Steve,
Have a look on my (sadly neglected) site www.audi200.org.uk and go to the technical area. There you will find a pdf relating to fault finding of the autocheck system.

Dry solder joints on the instrument cluster printed circuit board are the usual culprits (btdt) but worth going through the correct procedure if you can to establish the course of action.

Other than the aforementioned possible causes, I'd also say that audi wiring has a tendency for the outer wire sleeve to go brittle and crack, allowing moisture in and corrosion of the copper strand inside, or even just too much verdigris on the connectors at the pressure switches where they are crimped onto the wire.

Hope that helps.