Misfire on all cylinders

[petflunky]

Hi
I have an 05 Aveo that has a problem. Specifically, it misfires on all cylinders. This is because the engine is dumping fuel into all the cylinders, because it thinks the engine is cold. This is what I know from the mechanic working on it. 1. It has spark to all cylinders. 2. The cooling sensor on the back of the block is good. He checked it. I hooked up one of those computer things and it said that it was reading a coolant temp of -70 degrees, signaling something wrong with the sensor. Well it's not the sensor. Next thing is to check the wiring from the sensor to the computer. Anybody have any ideas what else it could be?

Thanks!