Possibly defective ECU - looking for technical information

Google search link....click here

https://www.hyundaiperformance.com/threads/ecu-pinout-diagram-for-1994-hyundai-excel.87164/

Good answer, if you’re a diy’r. And the part works.

Normally to have it replaced by a mechanic, the labor costs 10 times of what the part costs.

You need to find a local specialist to diagnose the problem....then opt for low cost option....

In the approximate 40 years of ECUs, the probability of the unit itself being possibly defective is so close to zero, that it is zero. If it’s bad, it is really bad and there is no doubt. Do what PWSlack suggests, pull one out of a junkyard and try it. Buy a ‘rebuilt’ one, as it has probably been exchanged several times with no effect, as it is likely something else.

Thanks to you and the many others who have responded. Currently the car runs but shifts oddly. After the girls' final exams it will go back in the shop to check problems with a solenoid in the transmission. Only when that is eliminated will the ECU come back under suspicion.

What does the code reader say? My ECU has a set of codes for the transmission and that may tell you something.

I justify have a code reader as a hobby, but I’ve found it to be a good investment. And being a hobby, where I don’t use it often, I bought it from HF.

I have a Bluetooth adapter for my OBD II and there are several really good apps that can talk to it with downloadable code sets for various vehicles. I use OBD Fusion which also gives me extra gauges while driving like mileage etc. Very cool.

Might just need to be cleaned and fluid and filter changed...

Is there a users/owners group for your vehicle? Almost every car problem has been encountered by someone before & they can offer advice. Try searching Google, Facebook etc.