My 1992 LS 1.8L Auto with AC upshifts and the engine runs smooth but the AT will not kick down a gear or two under a pedal-pressed attempt to accelerate. It throws codes 3 and 7 for the MAP and TPS. Replacing the MAP made no difference. I checked the TPS and determined it is NOT getting the required 5V feed voltage. Is there anything that might cause this failure to downshift other than a bad ECU? Has anyone had a similar problem? I have frequently changed my ATF and it is clean and the car downshifts as it slows down, just not when the pedal is depressed under a hard acceleration attempt. I’d hate to replace the ECU (hard to find and $$$) and find another issue. Any help appreciated!
This a super shot in the dark here, but several years ago, I had a funky situation like this. I can’t remember what codes the ECU stated, but what actually made things go wrong was a corroded positive battery cable and poor battery ground (under the battery). (I had some other things going weird like wipers / chimes too). Is ANYTHING else wrong? Regardless, those are easy things to check at least. Frankly, the issues I’m having now are just bad wiring all over the place 
Did you do any wiring tracing or discover any kinked wires from the ECU harness?
I will remove the battery and check the grounding wire. Thanks. I don’t want to pull the trigger on an ECU ($$$ with no returns) until I’ve tried anything and everything else suggested.
Checked - battery terminals and ground cable attachment A-OK and not the problem (heavy sigh). I am sending the ECU out for “repair” - $205 with shipping to repair, $99 inspection fee + $26 shipping if ECU is okay as is. I’ll report back.
What company did you use? I bought a new one from fs1inc.com .
I’m also wondering if it’s the separate transmission computer :-/
“if it’s the separate transmission computer”
Nononono . . . 
You are freaking me out!
With a quick inspection, there does not appear to be a TCM behind the driver’s side kick panel, just a fuse box. (“Belt warning control” box on the passenger side.) Isn’t the ECU an integrated unit that also controls the AT (1992)? I ordered the ECU repair service from Module Experts, a fraction of the cost of a new/rebuilt unit.
I have never heard of the transmission computer going bad. Just something else to look at given the age 
I’m just going off memory here. Let me take a look at the Helms when I get home. I could be mistaken.
I am pretty sure there is a gold box up in the fuse box area that would be your TCM. Hopefully the ECU sorts out your issue. Stay patient and rule that out first! When the trans is acting right, the auto is really a lot of fun to buzz around with in S3/S4.
It would appear the sole source of power to the TPS is via the ECM so if you’re having a power supply issue that is likely to be your source.
Just checked (learning as I go) and there is no 5V power to the MAP either.