Next day my check engine comes on i scanned it and get P0171 system running to lean. Not sure if it has anything to do with that I decided to make sure I seated everything properly. After that I decided to erase the check engine code to see if it would go away. I ran the check engine and tried to erase codes it erased the code but the the car wouldn't start and stated the transmission is not in park. Ok so I removed and reconnected the negative battery terminal to see if that would help. Sure enough it helped the car started but now it was shaky which it wasnt before. I scanned to check if another code had popped up and now i have code U0073 Control Module Communication Bus “A” Off. I am not sure what the scan tool did any ideas of thoughts on how to fix this?