What causes a bad PCM?

Answer 1

This answer was "borrowed" from "lesterl"; from the following web post: http://www.s10forum.com/forum/f104/why-does-ecm-pcm-go-bad-353612/

I claim no responsibility for poor grammar/spelling... Why does the computer go bad, let me see, how long does a normal Desktop computer last? Several things can kill a computer, #1 HEAT, #2 Shoddy Design, #3 Poor Regulation on Alternator, #4 Bad Connections, #5 Excessive Moisture, #6 Excessive Vibration, #7 AGE. I am sure I missed a few, but heat causes expansion and contraction and will allow components to pull free of their soldered in PCB state or cause a thermal breakdown of other components I.E. Capacitors are common, Electrical Spikes from power system if you jumpstart or bad regulator can damage internal IC's, Moisture can cause corrosion (primarily on connectors as PCBs have been dipped in an Ignition sealer (making the bad connections of IC's and such hard to resolder), Vibration can cause components to break away from their original locations, and just plain AGE gets everything in the end. Not to say any of these things will happen soon, it is just some possibilities, and Between you and Me these older ECMs are by far simpler than newer computer systems with multiple systems communication between each other like the PCM/ECM/BCM/VCM etc all having to talk to one another (multiple "brain boxes") for everything to work