O2 sensor terminology

[Ryd2live]

Just bought a used 04 Dodge Ram 2500 4X4 5.7L. 150K miles. At some point this truck was converted to dual exhaust. There are O2 sensors fore & aft of the cat converter on both exhausts.
The check engine light is on. It was checked at local Dodge Dealer. They said computer indicated " Banks 1 & 2 upstream O2 sensors are bad". Ok, so my question is which are the "upstream" senosors & what does it mean by banks 1 & 2 ? My assumption is bank 1 is one side & bank 2 is the other side.

 

[dodge dude94]

First off, welcome to the forum.

Secondly, you posted in the wrong section. You need to be in the third gen section.

However, I can answer your question. Upstream refers to the area of exhaust pipe BEFORE the cat(s). That is the pre-cat O2, the PCM uses those to determine the A/F ratio. The down stream O2 is what the PCM uses to determine if the cat is not doing its job, or on the later model trucks, to fine tune the A/F mixture even more.

Bank one will be the pipe for the driver's side, two will obviously be the passenger's side.


Hope this helps you.