Has anyone ever done this? What are the possible issues created by doing this? I had an old one for a 1996 2wd with a 5.9L that I had kept when I replaced it with a reprogrammed performance one. I no longer have that truck but I now have a 1996 4x4 with a 5.2L. The truck has been having some issues with slipping in gear at slow speeds and generally driving like it has no power. I noticed that both PCM units have the same connections so I swapped them. Now the truck runs better, but not like it should, just better overall. Will this hurt anything by keeping it this way or am I asking for trouble?

 

It probably won't cause any problems. You might find that eventually your truck will run the same as it did with the other PCM. Soon it will adapt to your engine and it's problems.

 

I wasn't sure. I would think that there could be a possibility of making this a performance mod since the 5.9L PCM would be trying to inject more fuel as it would for the larger engine into each of the smaller 5.2L engine cyclinders. As long as a more free flowing exhaust than stock as well as cooler and free flowing intake air was being used, that maybe it would actually make the smaller engine perform with a little more grunt... I am probably way off base here on what actually will happen, and I know that I'm only a backyard mechanic at best, but it would make sense, right? Maybe if a few more mods were made such as with the O2 sensors... Just thinking outloud...

 

I am sure the calibrations are different between the two engines. However, when running closed loop, the fuel tables my be able to adapt, assuming your O2 sensors are working correctly. I would be more worried about spark knock. As long as your not knocking, I would say you got lucky.