Hi all, I just joined this forum with hopes to find a solution to my car problems as well as to helping in anyway I can. I don’t know if any of you have experienced this issue that im having with my Upstream and downstream O2 sensors. I already bought replacement sensors but the trouble code keeps coming back.

 

Your problem is the heater control circuit... which controls BOTH heaters in the primary and secondary O2 sensors. There is a fuse for them... and it may not be marked on your fuse box cover. You will need to check a service manual for a full listing of the fused circuits.

 

There is an LAF fuse under the steering wheel and it checks good. The problem I’m seeing is that the ecm doesn’t send both negative pulse to the O2 heating element.

 

That is a different fuse. There is another fuse that will have power going to multiple circuits... including the primary and secondary heater circuits.

 

I will look for it but I do have battery voltage on the heater circuit with the ignition key on.