Not operational on UK S2 models. Believed NOT to be controlled from UK ECU as retrofitting bulb to Check Engine 'CAT' warning lamp location does not work. Confirmed true for 1994 UK S2 Coupe anyway. May or may not be true for other EU territories. 

I have an unconfirmed report that the Check Engine Lamp is operational on 1992 S2 Coupe destined for "KSA" - Kingdom of Saudi Arabia. 

More research is needed to determine if the check engine warning lamp can be made operational on non KSA territories. This would be a handy way to pull 'blink codes ' and has been documented for North American 20V-CQ and UrS4/S6 cars.

Latest research as of October 2002 shows that this is indeed possible. Details will be posted soon...

November 21st Update - Right here's the scoop on the MIL circuit. It is wired to the ECU. Just follow this link for a cheap and easy solution for adding the MIL circuit onto the S2 .

Believe all standard S2 instrumentation uses instantaneous fuel consumption in deference to the turbo boost display which is available on the URS4/S6 of the same generation.

Believe the RS2 is same in this respect. It's a pity because the ECU intrinsically knows the boost pressure and it is technically possible to have the info displayed on the autocheck system on the S2 family. For some odd reason the UrS4/S6 (or some of them anyway) DO provide boost pressure info in the Autocheck system. Unfortunately, the Autocheck computer in the UrS4/S6 is constructed in a completely different package which prevents it from being transferable to the S2.

There is a remote possibility that the ECU pin used to convey the boost signal is connectorised somewhere vaguely accessible in the S2 wiring loom, but the schematics do not give anything anyway in this regard.