jstooks

I have a 1995 Altima 2.4cyl with 190,000 miles. I was driving the other day and the check engine light came on. Car seemed to drive fine with no problems. I figured it was a sensor of some kind. I took it to the shop and they said it was the EGR, then they put plugs, wires, cap and button on it, but still didn't fix it. They informed me today that it had a short in the wiring harness and every code was coming up in the computer: O2 Sensor, Knock Sensor ect..... I know a little alot about cars for a girl....... I have worked on them since I was little, but my thinking is, if I had a short, wouldn't it slowly get to the point that wires are touching, and if there was a short wouldn't the car run like crap if every sensor was showing up in the computer. Or does the computer completly take over and just shut down those sensors? I am a little confused about this and anyone that can throw some suggestions out there would be greatly appreciated. I am going to take it somewhere else later this week, but first I thought I would ask you guys..