A 93 Rodeo has a 3.2 SOHC, I have the DOHC, but hopefully checking the codes is the same.

The ALDL is located behind and slightly lower than the stereo, toward the driver's side (near where your right calf sits as you're driving).
Mine is bundled together with two other connector thingies; there's a white one with 3 wires, a green one with 3 wires, and a smaller white one with only one wire. You want the white, 3 wire one.
With the key off, put a jumper wire on the two outboard terminals. Turn the key to "on" and the CEL flashes code 12 3X to tell you it's in diagnostic mode, then it'll flash each code 3X.

My experience has been that the code 32 (EGR) will set give me a CEL that goes off at idle and comes back on at ~1700 rpm. I clean out the EGR valve, vacuum lines and such, and it's good for another 8K miles or so. I thought maybe I had a weak ignition system or something, but my plugs are never fouled. <img src="/forums/images/graemlins/confused.gif" alt="" />