Check engine light, whats going on?

Hey everyone-

Just to preface, I have searched the forum and there are quite a few topics on this, but didnt find anything to quell my nerves.

Last Saturday, my check engine light came on while driving down the interstate. Not knowing what was going on, I found the nearest pep-boys just to make sure my car wasnt about to fall apart.

They checked the codes and it was giving a duplicated : P0036

I know that the code involves the sensors in the exhaust so Im looking to you guys to tell me what you think it is.


Just some background on the car: 2005 CTS 3.6 w/ 98500 miles. I also got a muffler/res delete back in december.

Thanks guys!