Oxygen sensor operation

Hi guys, I am in a need of some information on o2. GM 3800 with only upstream O2 system. I cannot make RH O2 go rich even with adding fuel. It goes way lean no problem. I switched the sensor from LH to Rh same result. Max volt is around 700 MV. Rh side doesn't cycle it's flat line 500-700 MV at all time. I even tried new sensor same result. I can make computer go over 1 volt by providing 12 volt on signal voltage via test light. Any help would be much appreciated . Thank you

Have you checked the heater circuit for supply and ground ?

Yes heater circuit has good power and ground. Thank you for your reply.

Can you pull the sensor voltage down by back probing the signal wire and using your body to ground the signal wire to the frame.

Yes I can pull it to low voltage like that no problem

Is the Buick running bad? Backprobe the pcm in the o2 sensor with multimeter see what your readings are. If the multimeter reads 1 volt or more and the pcm sees no Chang the pcm is bad

Was that voltage (500 - 700mv) measured in scanner or voltmeter?

On the scanner

I will do that thank you

You have already covered this by swapping the sensors over, but another way to check a conventional O2 sensor is to remove the sensor connect it to a multimeter and use a propane torch. Get it hot and move the torch around over the sensor so it is exposed to different parts of the flame and you should see the output voltage change.