OBDII code- cat. efficiency below threshold

recently, I had been driving my 97 Jimmy around with a messed up catalytic converter for about 4 or 5 months. It had all kinds of messed up codes on it, so I finally just took off the cat. and put a metal tube in place of it. I rechecked the codes, and there were still 4. one was cat. efficiency below threshold, then O2 sensor voltage below threshold Bank 1, and O2 sensor voltage below threshold bank2, and a code that said it was running lean. I replaced the O2 sensor before the cat. and that got rid of all the codes except the cat. efficiency below threshold one. could this be caused by the O2 sensor after the cat, or could it just be because I dont have a cat anymore?

efficiency below threshold one this prolly means the cat is not workn my guess is because it is not there

yea, thats what I was thinking. so is there anything you can think of that I can do to get the CES light to come off? I think I had heard something about O2 simulators or somethin like that, do u know anything about that?

Jack
The O2 Sensors each produce a voltage depending on the amount of oxygen left in the exhaust after combustion. The front sensor provides an input to the computer to correct the mixture by adjusting the injector "ON" times. The rear sensor checks the operation of the CAT and should read leaner then the front sensor. Since your converter is missing, they both should have the same reading, so the computer thinks the CAT is defective.
Better replace that CAT before your next smog check, or BIG FINE.
See ya
94