Where is the 02 sensor on 04 colorado

Those are your only codes? you really shouldnt have drilled out your cats, its hard to diag an 02 sensor online. a scanner could show if they are functioning properly. It might be an issue with your cats though and require replacement.

Id say hes right with the relay sensor

check air filter to see if its clean, spark plugs and wires, tire pressure make sure all tires have the correct pressure, wheel alignment will waste fuel. This is just a few things that come to mind. If check engine light is on go to any auto parts store, and they will read the problem code for free. If its on, you may have a bad 02 sensor. That may be the cause of high fuel consumption. Good-Day!

Take it to a qualified repair shop

PO441 ,PO442 codes have to do wit the oxagen sensors, If there is a problem with both of them,Or your cat is pluged up ,The car will not run (Properly)

check engine light on when tested it says bad o2 sensor did you replace 02 sensor it takes driveing it so many miles before light will go off give it couple days you dont need cadillac converter check engine light will go off cv joint they click as you turn dont let a mechanic sell you something you dont need its very rare for cadillac converters to go bad its common for o2 sensors to go bad like yours did but when 02 sensors are replaced it takes driveing it for awhile before it resets itself you also have more then one 02 sensor was then wrong one replaced they screw into your exaust manifold

Simply put anytime any check engine light comes on it is usually an indication of a slight malfunction happening within the engines emmisions system/sensors failure, etc.
If you dont want to purchase a hand held scanner for 100.00 take the vehicle into an Auto Zone Auto Parts Store and they will attach there scanner to your Diagnostic onboard connector link and read out the code or codes to you and give you a print out if needed to make the neccessary repairs to the engines computerized system, all for "FREE!!!

Bad Cat.

Cat could have collapsed and exhaust cant get out efficiently but i doubt a cat has failed or oxy sensor for that matter.Why change 1 injector?the vehicle is only 3 years old and should be under warranty it all sounds quite strange and with no other info or specific details i doubt youll get any intelligent answer.Sounds like a lot of people/places have fiddled with your car with no decent outcome?What was the original problem before taking it to auto shops and mechanics and having to replace an injector?

it could be that your fuel pump could be weak. or that it's in the electrical circuit of your fuel system. what that means is that the sensors that help read the performance of your fuel system could be malfunctioning. this would involve the O2(oxygen) the TPS(throttle position sensor. or it could be the fuel pressure regulater. you could probably go to a small garage and have scan done cheaper than if you take it to a dealership.hope this helps please rate this ......thanks and good luck