I hv an 08 na grand prix. I started it the other day and it ran like a bag of poop. I brang it In to the shop and it showed up with two codes. 171 & 300. Bank one running lean and multiple random misfire. The coil that feeds number 2 $5 coil pack wasn't firing. So I changed the coil with no luck. I chevked the pcv cleaned the tb. My battery terminals were corroded bad so I disconnected the battery cables to clean em up and now it won't start at all. It will turn over buf that's it. I started the first time after disconnecting the battery and it ran for 6 seconds and died.
I have no idea were to look now. Any help would be appreciated. It has 133000kms and well maintained.