newb question on 02 sensor...

[black2000dak]

A while back one of my buddies who is a tech for a dodge dealership hooked up the DRB to my truck (2000 3.9l v6 dakota) cause the engine light was coming on. He said the lower 02 sensor was shooting a code but didnt tell me the code.

Well now it is time to smog this puppy so I guess I have to fix it. I called the dealership to see if they have any in stock and they have one downstream. I assume the lower 02 sensor is the downstream sensor, would I be correct with that assumption?

I just want to be sure before I go pop 100.00 on the wrong sensor. Thanks in advanced.

[J_D]

Yes that would be correct but, it is possible that the cat is bad and the sensor is good .
My 2 cents.

[black2000dak]

cat was bad, it was already replaced and the lower 02 still shoots the code. Thanks for your response. I guess I will run up to dodge and buy it.