It looks like a box, kinda like the PCM, on my E99 it is inside the drivers fender well and I'd have to pull down the rubber fender skirt to get to it. Your 96 I think is in a different place, I hate to try and give any advice on something I'm not familiar with. Maybe search some posts on IDM's. Also I don't think there is a way to test it and since it makes something like 110 volts of DC power you better be careful with it or it might knock the crap out of you. Again I have no way of knowing that your IDM is bad, thats just a guess and probably what I'd try next. It would be better if you could borrow someone’s that is known good. If you do decide to buy one then I recommend car-parts.com for used electronic parts, I got my spare PCM from them for $75 delivered. It looks like if it were an IDM problem then you’d be getting IDM codes for it but stranger things have happened.