Suburban O2 Sensor Trouble

[joesregalproject]

So the 99 Suburban I bought a couple weeks ago has been great so far. I have had to put some money into it, but no major issues. One of the things I replaced was the entire exhaust from the manifolds to the muffler including both cats, as the exhaust that was on it was hacked together beyond repair and was leaking everywhere. I also replaced both downstream O2 sensors as there were codes for both of them and they broke upon removal. After completing the repairs, resetting the CEL, and driving about 3 miles, the CEL came back on. P0134 code, no activity detected bank 1 sensor 1. So I reset the CEL thinking it may have just been a glitch in the PCM after it detected the new parts. Today after driving it another 40 miles, the CEL came back on. This time P1133, insufficient switching bank 1 sensor 1.

I'm at a loss right now with what I should do. Should I replace the bank 1 upstream O2 sensor? Before changing the exhaust there was no code for the bank 1 upstream O2 sensor. Also I should mention the vehicle is running excellently and gas mileage has been improved since changing the exhaust and the downstream sensors. Any input is appreciated.

 

[pontiacgp]

I would check to make sure the wires are good and connectors are clean

and if you have the room to get underneath you can test it without removing it, let the engine heat it up and then test the volts on the O2