Transmission control module replacement, does it need to be reprogrammed?

Okay, with it going into limp mode and running badly, that could be the TCM but it's not real likely, as Doc says they are not really failure prone. From the sounds of it you need to find a shop that has an OBD I scan tool, that will actually pull the TCM codes to give you an idea where to look. A scan tool like the old Snap On MT2500 (the brick) or an OTC Genisys with the OBD I software and adapter plug. Some of the new tools claim to work with it as well, but I've only tested a couple. The connector for the system is an odd shaped 6 pin connector under the hood. Because it's OBDI most of the places that do free scans won't touch it, because it requires the older tools, or the special adapters. Find a place that can scan it and use the chart Doc provided to see if it is the TCM.

That is why you need to have it scanned; there is no way to know what is wrong at this point. Without looking at all the module information and any stored codes to see what the system is actually seeing as problems; you could replace every piece and still have the problem because it is something else. The TCM in that car controls the Transmission, it isn't going to cause the engine to run bad unless it is shorting out something else. However, a bad running engine could cause limp mode and shifting issues. That is why you need to find a scan tool that will work on that van and go from there.

Because it's a 94 you need one that can read the OBD version 1 codes and data. The ones for modern vehicles usually won't work unless they have adapters and the correct software. The 2 most popular aftermarket tools are the ones I mentioned earlier. The Snap-on MT2500 with Chrysler cartridge and the Genisys. There were others but those are the easier ones to find. There was also the Chrysler DRB II factory tool but those are harder to find in working condition. My Launch and Autel units both came with the adapters for OBDI but I've never used them as those are very rare vehicles where I am so I can't say how good they work on vintage vehicles.

You're demanding your doctor diagnose what's ailing you over the phone, but you refuse to go see him. The fault codes were designed to tell you in which circuit or system to start looking, otherwise everything is just a guess. That's the most expensive and least effective way to diagnose this problem.

If you're anywhere near northern Wisconsin, I would be happy to read the codes for you, but since they throw a pound of salt on an ounce of snow here, there aren't many '94 models, other than mine, running around. Another alternative to consider is to find a nearby community college with an Automotive program and talk with an instructor. We were always looking for live work to give our kids real-world learning experiences. The only possible drawback is we would only do this type of work when my Electrical class, or the other instructor's Engine Performance class were being taught. To try to do this during, say, Brakes class would take work away from the shops that hired our graduates, so we had to stick to the subjects currently being taught. It takes longer to dig out and connect the scanner than it does to actually read the codes. Within a couple of minutes we'll have an idea of how to proceed.

If you insist on replacing the Transmission Computer, look for a pick-your-own-parts salvage yard. In particular, I've been to 16 of "Pull-A-Part's" yards. They're all very clean and well-organized, parts are inexpensive, and employees and other customers have always been very friendly and helpful. You can do an internet search to see if there's a yard near you, and if they have a similar model in the yard. I bought a used Engine Computer for my '88 Grand Caravan a few years ago for only $25.00. There's a lot of similar yards popping up all over, but none are as clean as those at Pull-A-Part.

If you install a different computer and it continues to go into limp mode, it's doing what it's supposed to do. Then you'll be forced to have the fault codes read to know where to start the diagnosis.