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Message: <blockquote data-quote="clevor" data-source="post: 25361" data-attributes="member: 6998">So, it's been a while since I posted. My truck is fixed by my own hands but there was a lot of money spent to do it. Maybe more than I should have spent, but I'm inquisitive and even at 64 I want to learn something new, so this is what I did.I began to suspect that my scan tool was not working correctly (it was actually) and went to HFT and purchased an Icon T8. $900.00. but before that my original scan tool showed I might have a comms problem. The scan tool I had didn't seem to be able to check comms so I purchased a breakout box, test leads and a miniature oscilloscope from amazon. Total cost of that: $96.00. Testing with the breakout box and oscilloscope showed I didn't have a comm problem. This model truck uses a serial data 2 connection. Nice square wave with a little noise on it but working none the less. Took some time to figure out how to use the scope but it's a cute little tool. Fits in the palm of your hand. The breakout box was useful also as it was designed to check the DLC pins for proper grounds, voltages, serial data and can buss. Anyway, I saw nothing amiss with the checks I could do with this equipment. On to the scan tool. Like anything else new it took some time to figure out. But what that tool showed me was live data from the transmission. It was with this info that I found that the tcm had an internal voltage problem. 5.8vdc to be exact. I surmised that this problem caused all the other erroneous trouble codes which caused so much confusion on my part trying to narrow down what was going on. There was no problem with supply voltage going to the tcm as I monitored those with gauges. it was all internal. Live data showed that. So, I guessed that the tcm was bad. I hoped anyway. Went to Orielly's and ordered a rebuilt tcm. $400.00. It comes bare so internet research says it has to be flashed with vin and other data. More internet research says that in order to do this I have to have a pass thru device. After more internet research I chose Topdon J-2534 tool from Amazon for around $300.00. After more internet research I found that you have to get on GM website (ACDelcotds.com) and purchase a permission slip to download this data from their servers, $45.00. Then once that is purchased you get to download software which sets up MDI Manager on your computer along with Techline Connect. All this software is free but is a pain to get set up if you don't know what you're doing. which I didn't and took me 6 tries to get it to work. Also had problems with WIFI as truck was outside and router inside. Had to hold laptop up in air to get a good signal in the 95deg baking sun for seemed like ages. And now that's all done, I had to download software for the J-2534 and "bind" it to whatever. That was never clear to me what that was about, but it worked. So, everything is communicating correctly and now I'm ready to flash. You see why shops charge so much now! Following the directions and using a little guess work I was successful in flashing the tcm. No check engine light, drove truck and it seems fine. Was it worth the time and money? I don't know but I learned some new tricks. Hope this helps you.</blockquote>