Need help-1991 Mighty Max Auto Overdrive

[ChiPop73]

I own a 1991 Mighty Max 2.4L engine with an auto trans that has overdrive.
Problem is tranny shifts out of overdrive into 3rd, and at same time red check engine light come on dash. Then after a short while, or a long while, it shifts back into overdrive. No rhyme or reason. does not matter if engine is warm or cold, or if outside temp is cold or hot.
It will sometimes go for days with no problem...usually messes up a lot.
Took it to the Mitsubishi house and their computer cannot talk to my on-board computer because they upgraded their software and can no longer diagnose a 1991 model. We did change out a couple of very expensive modules...no help.
Any ideas?

[rxinhed]

There are a few water temp sensors that could be the culprit here. Check the tech board on 4x4wire?

[ChiPop73]

Originally Posted by rxinhed

There are a few water temp sensors that could be the culprit here. Check the tech board on 4x4wire?

I have not checked 4x4wire...but I will...thanks for the tip.