Who stoll my O2 sensor ?

[zyka1]

after getting bad milage on my 2000 Yukon 5.3L I fully flusshed out the fuel system , seafoamed it, replaced the spark pluygs and leads and change and changed the fuel pressure regulator valve. Not much inprovement.

So i thought changging the O2 sensors and Cat would be a good idea.

went under the truck and What!! no O2 sensors or Cat. just a straight set of pipes from the exhuast manifolds into the muffler. What up ?
so i checked Gm online. 4 sensors and 2 cats. but i got none.

I bought this yukon second hand.
I think someone has ripped out the original exhuast system and replaced it with out a O2 sensors or cats.

Can some one help me out here, i starting to go nuts.
DO i need them? there are two fuses in the fuse bay, but no sensors.

strange thing, not a single code is coming up. I dont know whats up.

I have attached a few pics of the place i think they should be.

I would appreciate the help!

 

[smurphy80]

the first picture...you are looking right at one of the O2 sensor

second picture is so small...but looks like one the Cats to me just in the upper right of photo

 

[dwmmatt23]

yea that looks like one of your cats in the second pic and thats definately an 02 in the first pic, if your not getting any codes its because they are still there and running fine or if they are gone like you said someone tuned out the rear sensors. Alot of people (if you live out of california unlike me) do delete there cats and run straight pipes and tune out there rear sensors. but it looks like you might still have them

 

[jhellwig]

The sensors can be going bad and still not throw codes. If you have a code scanned you can watch the voltage from the sensors. If they are good both banks will fluctuate fairly close with each other in a rhythm. If they are bad they will bounce in different directions and do odd things.