2003 Pathfinder O2 sensors? which 1 or 2 should i buy??

seems like a easy install however choosing the right ones seems difficult lol so many opitons, downstream or upstream, left right. just confused thanks

any help appreciated

cheers

The upstream O2 sensors (the ones before exhaust flows into the cats) are the most critical. These play a role in air/fuel mixture, constantly sending rapidly changing voltage signals to make the fuel input leaner or richer. The downstream O2 sensors (the ones after the cats) do not effect air/fuel mixture. Their voltage signals, which are far less variable than the upstream sensors, monitor how effective the cats are performing. Since our Pathfinders use four O2 sensors, replacing all of them at the same time (which is preferable for overall engine performance stability) can be very expensive purchasing quality replacements. That being said, if budget is an issue, and to address your specific too lean/too rich fault codes you posted about earlier, I would opt for replacing both of the upstream O2 sensors if you still have the original 16 year old ones installed. When I bought my '02 Pathfinder used from a dealership, it had its check engine light on which turned out to be a faulty O2 sensor. The dealership replaced it with a Bosch sensor. I have since replaced the other 3 sensors with Bosch. Since Bosch invented the automotive O2 sensor more than 40 years ago and the dealership used them for replacements, I figured they were reliable enough. Warranty length and price points of various brands should give you some idea of getting what you pay for. As for your downstream O2 sensors, and maybe some of your confusion, there are 2 different types for each exhaust side on an '03 Pathfinder. The ones you would need depend on when your '03 was built. The driver side door jam sticker will give you the manufacture date of your '03. Your upstream sensors have only one type for each exhaust side no matter when your '03 was built.

appreciated the reply man, much appreciated.... are the BOSCH ones universal? i found on rock auto - BOSCH 15665

They are not universal. The wire length and plug connector are specifically made for the intended use. This one for instance, (Bosch 15665) only has a wire length long enough to reach where it is intended to plug into its mate when installed as the upstream passenger side O2 sensor on a '03 Pathfinder. The plug style is also specific to its intended use and fit into its mate.

cool man, thanks for the info. goes a long way.

made the order, see how it works out

again thank you