Check engine light so checked with tool and PO138 upstream sensor. Went on eBay and it show 3 of them and some just 2. So my question is is it two ( up & down) or 3? 1999 Dodge ram 1500 5.2L 2 wheel drive. My plan is to replace them all this weekend but thought there was only two so this threw me off. Seems like a dumb question but have to ask. Thanks

 

Might want to review the information in this thread - https://dodgeforum.com/forum/2nd-gen...ode-po138.html

If you do decide to replace the sensor, please be sure to use an NTK sensor.

 

And ebay should be the last place you go for parts.

 

This. OP, B1S2 is not an upstream sensor

 

I'm going to check out NAPA but where I was confused is showing 3. To my knowledge I thought there was only two up and down. Before and after Cat.

 

I just looked up auto parts stores local and NTK aren't available in store pick up and I'm not sure if they can be ordered? How are the Bosh ones?

 

Bosch suck, and these trucks just don't like 'em. Denso or NTK only please. If that store doesn't have one or the other, call around.

 

Ok, Thanks. I will see about Denso.

 

Mine showed there was a longer rear one depending on the configuration of the truck.Same sensor just with a longer lead.

 

Well it looks like I will have to replace up stream this weekend , then down stream next weekend. This will also allow me to check them all and what I would need. I believe this is the first time they have even needed to be changed. lol