how often do computers go bad??

The car is a 93 and the coolant fans aren't kicking on, i check everything and the problem is the part of the relay which gets grounded by the ecm. The computer isn't grounding it for some reason, both the coolant temps sensors are new so i know that's not the prob. I'm thinking maybe the computer is bad, neither the low nor the high will kick in. I know i can always through a manual fan switch in but if it's possibly the ecm i will just change it out.

I just checked by jumpering terminals a and b on the aldl connection and the fans will turn on, i checked the connections at the coolant temp sensors and they're good, i'm confused, if the computer was bad wouldn't the coolant fans not turn on when the terminals were jumpered???