Computer system?

You'll need a professional scan tool to be able to read the modules that control those things.

Nobody knows until they get into it and see where it leads.

About the only thing you can do yourself is to use an inexpensive digital voltmeter to measure battery voltage while the engine is running. It must be between 13.75 and 14.75 volts. If it is low, suspect the generator. Since the '87 models, GM has had a huge problem with them developing high voltage spikes and with repeat failures. To prevent both, replace the perfectly good battery at the same time. As they age they lose their ability to dampen and absorb those spikes. Besides damaging the internal voltage regulator and diodes, those spikes radiate voltage spikes into the wires taking sensor signals to the computers. That can cause multiple electrical problems.

Another common problem is loose or corroded ground wires, especially where multiple wires are bolted together. Finding those is best left to the professionals. There are many ground wires and locations on the car. I don't want you to have it torn apart and still not find the problem.