Last year, I swapped a 350 from a 91 Z28 into my 89 Formula 'bird that originally had the 305 TBI. At the time, I didn't fully understand the re-pinning of the TBI harness to work with the new motor - I didn't realize the new motor was batch fired too. So, I ended up hacking my old TBI harness up and splicing it into the new one, re-pinning where necessary, both under the dash AND under the master cylinder.

I did manage to get the car running and it drives great. My only issue is that there is no way to plug in to the ALDL link and read any codes. It's not an 89 5.0 nor is it a 91 5.7 when you plug in. The reader doesn't know what to expect (and I've tried expensive auto-shop readers, not just the part-store testers).

That brings me to the question, if I re-do my wire harness by re-pinning an actual TBI harness and convert it to the TPI, will I be able to read any ALDL codes, or just by the nature of swapping motors from different years, have I removed that feature from my car?

 

Pin BA8 (orange wire) at the ecm is the data serial line. Connect yourself a wire there and put a spade connector on the end. Then just run another wire and ground it somewhere with a spade on it. There ya go. Connect those the the proper pins on your ALDL scanning cable and your good to go.

 

The orange wire on a TBI is in the "E" position on the ALDL.
Move it to the "M" position if you want to read Data on a TPI system.

 

I was assuming he already tried switching out the wires at the ALDL connector. I was referring to actually connecting directly to the ecm.

 

Thank you all for the info. I'm not sure if my son has swapped any pins yet (I don't think so because he was having trouble finding the info). When he wakes the beast from it's snowy hibernation here in Michigan, we'll check this out!

Reading the above posts, am I correctly understanding that if he makes up a "new" engine harness as described in the TPI Engine Swap post, and then makes the above change to pins E & M, he should be able to just plug in and read the engine codes from the car's computer? Also, he would also enter the MOTOR'S year into the scanner tool, not the car, right?