Where is the o2 sensor on a chevy avalanche and how many are there

SOURCE: have 2002 chevy avalanche 1500

sounds like a sensor is loose maybe not have good contacts?

SOURCE: This code keeps coming up

This could be due to the wrong O2 sensor, Bad Catalytic Convertor, EGR valve or something along those lines. Did you replace this with an OEM part and not have to change the wiring harness or did you have to change the wirings? The other most common issue is you changed it with a non-OEM product and the O2 sensor is not reading correctly. Check to make sure wires are hooked up correctly. Also not know the details of this vehicle it can be that you changed the wrong O2 sensor also, most vehicles have an O2 sensor before and after the Catalytic Convertor