Yep, that's correct in that the 91 is OBD I and the 97 and 99 are OBD II.

There is no scanner needed for the 91. There's a jumper (under driver's kick panel, I believe) that you hook up with the key off. Then you turn the key to the on position, but do not start it. The check engine light will flash code 12 (1 longer flash followed by 2 shorter flashes) 3 times saying that it's in diagnostic mode, then it fill show any codes that are stored, then repeat the whole loop. Then you turn the key off and unhook the wires when done.

For the 97 and 99, you will have to have an OBD II scanner. My dad bought one from Autozone a while back and it's done what we've needed and isn't too bad. I believe it was a Sun (?) manufacturing product. The other that I've personally used was I believe an Auto X-Ray (?) unit. I used that when I worked for O'Reilly's. It's a pretty decent product, though a little pricey (at least for me) if you're going to buy it. It was about $200 and up.

Richard <img src="/forums/images/graemlins/patriot.gif" alt="" />