hey guys i have a 06 envoy I6. my wife was in town the other day .after shopping she went to fire it up and no start. i went in the next day to try and figure it out ,but it fired right up. so i drove 40 miles back home with no problems an shut it down for the night got in it the next day and it just wont start. it has a new bat. alt. i checked the fuel pressure it s at 54. ran my code reader P2176 and P1516 came back. no check engine light flashing at all. im hoping you guys can lend me a hand to figure this out. im not new to fixing my own rides iv been a long time s-10 owner and i can keep them alive just fine, we just upgraded to the envoy for the room. its really nice for us but we just dont have the cash to send it to a shop. any ideas what i should be or could check to get back up and running? i would really appreciate it thank you in advance.