So when I said I drove my new super NP craigslist truck home without “major” mishap, that “major” qualifier was crucial because I omitted the MIL coming on about 15 minutes into the drive.
I thought I needed an OBD-I to OBD-II cable to check this out, but I learned from the Haynes manual that you only need to jam a wire between the two top rightmost ports of the OBD-I socket and the MIL will flash out a decimal code you can look up.
After borrowing a jumper wire from my current breadboard project I obtained code 43, which indicates a problem with the Electronic Spark Control module (the thing that retards the timing based on input from the knock sensor). On this generation it’s a whole distinct module, not something the ECM does.
So tonight I’ll be making sure the connector is seated properly and testing all the wires to & from the module that I can. The Haynes manual says you can test the resistance of the module itself to see if it’s good but is of course extremely vague about, you know, which terminal on the module to test. So maybe I’ll figure out how to do that, or just try all of them and see if any have the right resistance. If that doesn’t work then it’s off to grab one of these from the junkyard this weekend.