I had a similar problem. The car would become hard to start and eventually the Check Engine idiot light would illuminate. I'd have a local parts store pull the code and it would come up as a failed crank position sensor. I bet I bought a half dozen of them and had a dealer install them. I got tired of this. I finally found a dealer with a MECHANIC who could do more than hang parts. The underlying problem was a chafed wire. He fixed that wire over a year ago and the problem has not re-occurred.