There is, or was, a code reader for the Renix system, and I believe there is still a module available for certain Snap-on rigs, but it's prohibitively expensive, since you need the basic unit as well as the plug-ins. No codes are stored, but the computer sends out a serial signal while it's running. If you search this forum hard enough, I think you'll come up with someone, I forget who, who actually possesses such a Snap-on kit. Jon "5-90" has been hoping to figure out how to hack the serial output, but I guess he hasn't got there yet. The problem, of course, is that even if you get a signal, you need to know what the numbers mean, and that information doesn't seem to be floating around. Unless you can find someplace that has the scanner, the best bet for now is, as stated above, to diagnose the individual sensors and components. But you might just hunt around for an independent garage that has a good diagnostic system and see if one of them has the Jeep module. They're out there somewhere.
The idea of a GM computer seems like an interesting one, although it also seems more trouble than it's worth. I have a Chilton fuel injection book that states (incorrectly, it seems) that all 6 Renix injectors are fired simultaneously. It does raise the question of whether such a system would work. If you were able, for example, to split the firing of the six into groups of three, timed simply so that no injector would fire into an open valve (ideally, the injector should fire at a closed intake valve just before it opens), I wonder how it would perform? I agree about the GM diagnostics. I found a plug-in code reader for my 88 Chevy truck at a tag sale for five bucks. It still just blinks lights, but now I don't even need the paper clip to tell me the oxygen sensor wire has rotted off again.
