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I'm probably going to at least ATTEMPT to try and develop a homebrew TCU. But first, I'd like to have what the common issue with the TCU's, and what makes them $#!& the bed. Is it a hardware issue? Is it a software issue? Has anybody else attempted this? I am fairly new to this forum, and I'm sure a lot of you fellas have already looked at the threads way more than I have, but again, I'd like to troubleshoot the problem so I can decide how far I want to take this. If it works out, I'd like to post the entire process and open-source it so people don't get scalped on renix TCU's. A build list, an assembly guide, and a cost amount, assuming that this would come to fruition. Any help would be appreciated. Thanks in advance.

Hello, first post, before I discuss the issues, I've tried my best to look at most of the forum for a solution. I have an 87' Comanche, 2WD automatic, 4.0 inline 6. I was at the gas station, pulled in just fine, got my dranky drank, and when I went to pull out, reverse worked fine, put it into D, and I had no power whatsoever. I pulled my TCU out, and I still had the same issue, I have to manually shift it from 2-1 to D. And when put it in D, it starts off in 3rd, doesn't up or down shift. Reading online, I've seen a couple of things as far replacing the TCU, replacing that TPS, stuff like that. I have a new TCU lined up hopefully, however I just replaced the TPS after diagnosing the last one. When the TPS was relaxed, it was reading 4.8 volts. Switched out the new one, and the open throttle position shows me 4.8V. I guess my first question would be, How do I diagnose the TCU with a multimeter? How do I know if my new TPS was installed correctly? And is my transmission just shot? I've been after this for months, my mechanical knowledge extends to replacing an alternator on my dad's comanche, and an actuator, so I'm learning from scratch here. I'd appreciate any feedback, tips, etc.. Thank you in advance.