Does the values read by the o2 sensors after the catalytic convertor effect and cause the car to adjust it's fuel ratio like the way the pre-cat AFR sensor does? I've been reading up a bit on it and it seems that the post-cat o2 sensor creates a voltage between 0.1 and 0.9V depending on the amount of oxygen it detects. Is this just used purely to monitor the cats efficiency or does this data somehow cause the car to make adjustments on fuel trims etc? I know the AFR pre-cat sensor is responsible for constantly adjusting fuel air ratio, but wonderng if the post-cat one effects it. If i was to just put a dummy voltage signal on the post-cat to turn off cat efficiency errors, will it cause a lean or rich mixture etc?

 

If you have good, working downstream O2 sensors and continue to get CELs due to aftermarket exhaust components, I'd recommend one of the many available versions of these to fool the system :

 

When the engine is at a fixed state like cruising at 55mph the ECU keeps the air fuel ratio around 14.7:1 and varies it up and down +/- 0.1 so the CATs maintain their efficiency. So yes, they do influence the ECUs decision making as I know it and solely to help the 3 stage CATs reburn as cleanly as possible.

 

Thank you @2013FSport very knowledgable as always.

Sorry i'm not too technical so trying to understand it. So i've recently been reading about people installing o2 simulators for downstream only sensors where either they doing this because they have aftermarket systems or have done cat deletes or have cat efficiency issues. The o2 simulator seems to create a waveform where voltage is switched from 0.7v to 0.0v every 3-4 seconds. But the question is if the ECM does use this data to adjust fuel like it does with the main Air Fuel ratio sensor then can this not cause issues? I've read that the main o2 sensor that deals with the critical air fuel ratio mapping is the pre-cat sensor.