hi, i have the follow code for my '96 3.8....P0420 Three Way Catalytic Converter (TWC) system low efficiency Bank 1. assuming the problem is the oxygen sensor and not the cat, the sensor this code refers to is the drivers side sensor in the manifold (not the sensor just before the cat), is this correct? can someone please clairfy this for sure? if this is the manifold sensors i'm just going to change out both, i've never changed any of the O2 sensors. also, has anyone ever used walker sensors or heard negative feedback about them? where is the cheapest place to get delco sensors? any help is appreciated. thanks

 

Hey, I know this is kind of an old post but I was wondering what you found out about your car. I just found out that my car is giving the same code and I was wanting to know if it was your O2 sensor or was it your catalytic convertor?

 

Most muffler shops can test cat efficiency. Most likely the problem is the sensor.