WELCOME TO TDS,, if your SES light came on, there are codes. AutoZones reader may not see them, (Not all "Cheapo" readers will work on our trucks) Find someone with a Tuner and code reader near you maybe? Or someone with AutoEnginuity computer program maybe.
It SOUNDS like the CPS, but I would NOT buy Two now, maybe get one and install it to see if the problem recurs, but if it isnt then you have TWO spares, and wouldnt need that much money layin in your glove box... /ubbthreads/images/graemlins/rolleyes.gif Really being under warranty take it to the dealer, EVEN if it is the CPS costs you the 100.00 deductible, it is not much more than buying one your self, and you KNOW what they found. (Tell them you want to know what codes it has and all..) Also you want the old part back maybe? So if the problem is not fixed then your old CPS could still be your spare???? Just a thought.