I have replaced my O2 Sensors twice now on my 09 SC. LM320 I clear the codes but they return shortly their after. I have swapped out to another set of Sensors after being told that they may be not the correct type being after market. So the second set I bought from Atlantic British here in the USA and installed them. They are an Off brand called Walker.

My CEL is on constantly and even after I reset it it will return shortly their after.

I contacted AB and they told me that the sensors can't all be bad ?

I am going to try probing the harness and see if there is possibly faulty wiring between the O2 sensors and the ECU.

Any suggestions would be greatly appreciated.