And that's a wildly jumping voltage signal, right? Because the rear one was doing that when I checked it a few weeks ago.

 

Fuel trims are good enough, you don't have a fuel pressure issue, otherwise we'd be seeing other codes, lean or rich condition, is the cat on the car now OEM? If so, replace it, if it's not replace it with OEM.

 

Does it have to be an OEM converter? It costs over $500 and we don't have anywhere near that kind of money.

 

Voltage fluctuates at same frequency as primary O2 sensor (1-2 cycles per second) at a fast idle and amplitude will be from low 0.2 to high 0.8 V.

good luck

 

I thought the aft sensor was supposed to have a slowly changing value over a smaller range?

 

Yes, the rear sensor signal should be close to flat, if it reacts the same as the front O2 sensor, that tells the PCM the oxygen storage capacity of the catalyst is depleted and it needs replacement....if you have had this code since you acquired the car, I'll assume you live in a state that does not require any type of emissions testing. If that's the case have a muffler shop slap on a universal convertor...but don't be surprised if the light comes back on shortly after.

 

What about OEM grade? Would that work as well as OEM?

 

Just me but a good name brand converter will be fine. They come with a warranty as long as you follow the "documents"......meaning they might want to verify that the O2's sensors are working/been replaced and that.

 

This reply was for a failed secondary O2 sensor.

good luck

 

I'll replace the converter and both O2 sensors. Hopefully that will clear it all up for a while.