Hi Kelly.
I had the same thing go wrong on my g6. After taking it to a shop here in my home town, and an hour and half later I was told it was my upper cam shaft sencer, witch is located on top of the engine on the passenger side. There are two side by side. One is for the lower and one is for the upper. I replaced the upper one and it fixed this issue. A few days later I replaced the lower one and if had no issue after. I looked around on the net and there was no info about this. Or even at the dealership. I hope this helps for anyone that is having this same type of issues with there G6.
Kim