Had it scanned at Autozone and it said large evaporative system leak and O2 sensor malfunction. I looked at the gas cap and it looks good and is unvented type. Where is the charcoal canister or is there even one? I can't find any evap sys hoses in the engine compartment. I'll look under the car next. I'm assuming the O2 malfunction will go away if I fix the evap sys leak. Is this a common trouble?