Hard start up and engine light on
 

Hi guys.
I have a 2011 SRX 3.0L having problems with start up and the engine light is on
Dealer is telling me the i have a valve problem low compression in piston in #2 and they recommend a head replacement that make no since. so i took the car because it sound to be an scam to me.
I plug an scanner and it show to have a code P0340 and P0345 when i look it up it show to have problems with can sensor but there is 4, any advice here