Transmission not shifting properly and check engine light turns on?

This could be a not so complicated issue or a transmission out of car repair without some basic tests wouldn't know what comes next. In my experience either when the transmission gets warm and fluid gets thinner it aggravates a leaking 3rd gear piston leaking or creates a even worse low transmission line pressure issue. Or the transmission gets warm abs causes the 3rd gear solenoid to fail or the solenoid buss plate to fail or one of the wires to the bus plate to fail.

Yes still without doing some tests we can't figure out what's going on the transmission. It could get more complicated and would need more tools to further diagnose but first a multi meter.

If you're thinking about just replacing the 3rd gear solenoid, I would not, the line pressure being low is petty common on those. Plus, the bad solenoid bus plate is not that uncommon or the bad wires to the buss plate etc. Thats why I mentioned them and said tests needed to be performed. Unfortunately, this is one of those 90 percent sure or a good chance and worth the try. To replace the solenoid, you're going to have to take some stuff off to get to where it is. To replace it you have to take the top cover off the valve body. You will need a 1/4" torque wrench to put it back together.

Just giving you a warning, the next step would require more tools and tests if nothing is found with a multi meter plus hopefully it acts up long enough to catch it in the act.

The quad module is part of the PCM and not part of the transmission controls. Also, I remember the early years of working for Saturn people would get a code 26 in the engine control module which is a quad driver fault. People would call into the parts department wanting to buy a quad driver module. When the real problem is just a component on the quad driver circuit.