Electronic power steering goes hard

I'm assuming you are talking about Chevy's Electronic Power Assist. If the steering goes "hard" then the Power Steering has gone out. This makes it very hard to turn the wheel if you are not moving or at the very least if you *are* moving you will notice a marked increase in the stiffness of the steering wheel. Having the dealership replace the module will help, although it seems the problem often times returns 6 months to a year later.

I've had mine replaced 2 times in less than 2 years.