After my engine swap from a '88 TBI 305 to a '91 SD TPI 350 The ALDL port does not seem to be giving me any codes. The SES light came on the other day when I was driving home but I can't seem to retrieve the codes. I took a paperclip and put it between the A and B connnectors and nothing. Is there any wiring diffences between the 2 ALDL ports that would cause this. Any help would be great. Thanks in advance.

Jim

 

Nope. The A and B pins remain the same. The only real difference between those two years as far as the ALDL pins are concerned, is that in '88 you could power the fuel pump via the ALDL for testing purposes, where in 91 they had a seperate test connector.

Break out the multimeter, and test pin A to find out if it's a legitimate ground (touch A with one lead and a good ground with the other). Then access the ECM, pull the green plug from the ECM. The pins on the plug are numbered. Test for continuity from pin B on the ALDL, to pin GE12 on the ECM connector. Looking at the ECM plug, you'll see a tiny "12" next to the pin. GE12 is the side closer to the little plastic tang that you have to depress to pull the connector out of the ECM.

If you get continuity, I don't know what to tell you.. It should work. If you don't, then you have to find the break in the circuit. I would start with the clear IP connector near the ECM, and check out pin E on it. From E (clear IP connector) to GE12 on the ECM should be good. And from E (black IP connector) to pin B on the ALDL should be good.