GM-GMC: 2007 Canyon, coolant temperature sensor, engine coolant temperature sensor

Question
QUESTION: I have a 2007 GMC Canyon that I bought new.  It has 11,000 miles on it.  The check engine light has now come on for the third time.  the dealer can't find the problem.  They replaced the gas cap 1 year ago. Now, 1 year later, the check engine light is on again!!  Any solutions?
Thank you.

ANSWER: The way systmes are set up now days there are thousands of reasons that a service engine soon light could come on.  Granted, some are more common than others, emmissions being one of those.  If the gas cap does not seal the tank, through a series of test while driving the computer detects that the tank is not sealed and will turn on the check engine light.  It is entirely possible that when you fueled up last the cap wasn't tightened fully and after those test were run, the engine light came on.  Or it could be something completely unrelated like your engine coolant temperature sensor?!  Without knowing what the code is it is impossible to say what the solution is.  If I were in your position I think tightening the gas cap fully then disconnecting the battery for a half hour or so is a reasonable first step.  If the light comes on again you will need to have it looked at.
Hope this helps

---------- FOLLOW-UP ----------

QUESTION: The code that is being stored is PO442.  One year ago the dealer put on a new gas cap, because they couldn't find any problems, so this was a cheap thing to try. So, it's been fine for a year, now the code has come up again, and no problems with the truck can be found.
Thanks for your help.

Answer
P0442 is a code for the evap emmissions system.  If your truck is still under warranty, definately take it in and tell them (politetly) that you would like a rental car until it is fixed properly.  If its not under warranty, you can try what I suggested before or find a repair shop that you trust, and have them run the diagnostics for that code.  That usually means pressurizing the system with a smoke solution and watching for leaks.  I understand how frustrating it can be, you pay good money for a vehicle and the service that should go with it is sometimes less than perfect.  I can assure of one thing, you will catch more flies with honey than vinegar.  If you go back to the dealership, ask to speak to the service manager and explain exactly what the problem is, they may accomodate you if it is out of warranty.
Hope this helps