On account of the fact that the Autocheck computer was used on many 80/90 models of various engine sizes, weights and country specific variations, Audi took the wise approach of a modular design for the Autocheck system. This is much cheaper (and easier logistically) than producing specific systems for each country and/or engine and/or chassis type.

This material is fluid right now as I am still in the process of collating it, but here is some info, hints and allegations that are of interest...

First off, there are at least two physical variants of the Autocheck computer module that are applicable to the S2. Despite all the modularity designed into them - the LCD modules have a printed legend relative to Miles & Gallons (for the British Isles) or Kilometres & Litres (for everywhere else). My investigations are with the 'GB' coded Autocheck system, but I fully expect there to be other secrets with respect to cars destined for other regions. The table below gives part numbers of known Autocheck systems.

Country/Region	Autocheck Part
EUROPE (Display legend for km and litres)	8A0 919 067 A
UK (Display legend for miles and gallons)	8A0 919 067

Now things get really interesting, because although the S2 was never imported to the USA, it uses the exact same Autocheck computer model (a532) as the 20V Coupe Quattro which did make it's official way to North America. Now you'd think that because the Brits and the Yanks speak the same lingo and have resisted all attempts to understand kilometres, they would have the same Autocheck configuration... but you'd be wrong because imperial gallons (used in the UK) are larger than US gallons!

Consequently the trip computer has to make adjustments to fuel calculations accordingly. The way it does this is via a 'coding plug' which is inserted into an 11-pin connector on the Autocheck module.

It is the use of this coding plug inserted into the Autocheck module which provides it with information on the vehicle model and destination country that defines how the module behaves in any given application. The code plug, residing on the left edge of the instrument cluster, is shown in the figure below.

At first this trivial stuff would seem to be of little interest, but apart from the challenge of trying to reverse engineer it, there is one thing that the 80/90 vehicles do in some countries but not in others. This is the use of one of the 3x3 warning lamps to operate as a Malfunction Indicator Lamp (MIL) when the ECU has fault codes it wishes to report. This is alleged to work on Californian 20V-CQs and the coding plug is thought to be involved in enabling this function. I also heard that it works on Saudi Arabian cars, but this is unconfirmed. UPDATE - Coding plug is NOT part of the circuit to control any of these 3x3 warning lamps. Full details on the MIL circuit are provided here .

The table below details some known coding plugs from various 80/90 vehicles & countries. Eventually I hope to work out how to modify the UK-S2 code plug to enable the MIL bulb (as used on Californian cars) but retain the use of imperial gallons for fuel and range calculations. UPDATE - this simple mod is now working on my car for built-in blink code display :) It transpires that the coding plug has nothing to do with this functionality whatsoever. Details are here ...

There are plenty of other code plugs applicable to the Autocheck system. I would be delighted to add such details onto this part of the site - particularly from S2 owners outside of the UK - Please Email your codeplug part numbers if you can spare a few minutes to remove your instrument cluster. The Audi parts database does not list all of the country specific plugs so I need them from real cars so I can continue with the reverse engineering...

The code plug versions I imagine for the S2 should be for Saudia Arabia (SA), Europe (EU) and Japan (JA). Perhaps the South African and Australisian cars had their own code plugs too ?

Thanks to Maarten Reinders for the EU code plug info.

Well I think that is it's main purpose, but it could also be thought as an option switch which may do different things depending on the code plug that is being used.

When the instrument cluster is removed, a six positioned sliding switch can be seen at the lower left edge of the cluster - just round the corner from the code plug. It is unclear if this makes any effect on the fuel/range calculations but it does alter the behaviour of the Autocheck display. On the UK S2, this switch is set in position 3 notated as 'RW' - presumably for 'rest of world'. But changing it to positions 1 or 2 has an immediate effect when the ignition is turned ON as shown in the table below. Positions 4-6 seem to be for diesel engined cars which we don't ever talk about here !

I also noted that the US position provides a slight difference in the Autocheck self-test sequence . Photos to follow, but the US position lacks the hydraulic/brake system warning symbol at the start of the display test routine for reasons unknown - maybe the US market dictates that such a fault must only be reported by the most simple of means in the form of a computer-free warning bulb ?

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