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4l80e swap

JonnyB872 said:
Paid over $600, still no OD. Took it back to the shop the next morning, explained and the owner said "Sorry, we've done all we can do." Then sent me on my way.
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Bluntly they owe you a refund. They didn't fix it and charged you money. Last 4L80E I got rebuilt was around $1100, so, that $600 is painful. Small claims court if you have too esp. if another shop "fixes" it giving you proof. Keep your mouth shut at new shop about last place. Next place "starts over" with zero assumptions at first.

So you can pull codes with a paperclip and see if the ECM is complaining about anything. I am fuzzy about stuff this old, but, in general if the ENGINE is not running correctly the ECM unlocks the torque converter to reduce engine load: both as a stall saver and as an emissions reduction.

You may need to work the phones to fine a place that has the old scanners. I suggest you even call your local GM dealers. $100 or so to do a diagnostic.
 
Looks Same as other hummers and pickups. The engine control functions aren’t used. In 95 and older hummers and 93 and older pickups it is called a tcm- transmission control module/ newer they are called ecm engine control module. One of the things gm did smart- they knew they would soon be doing engine nonsense and built it for both from the beginning. My understanding is an ecm can be altered to be a tcm, but not the other way around. So Jonny’s tcm and mine should be same if my memory is right.
 
Your problem is the 91 PCM doesn't give a good data stream. The old GM tech1 works, but they are PAINFULLY slow, my tech2 reads 3 times as fast on obd1 trucks as a tech1 does. Then(as you have learned) you have to find somebody who knows what they're looking at. I'm not sure about your abilities, but the best scanning software for the money is diy based through tuner pro. You get a cable to connect to your laptop and do it that way. It's been so long since I needed something like that I don't know where to send you as I use my tech2 for everything
 
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