Just a quick heads up if you have a 2001 Pathfinder or QX4 and are in the market for new oxygen sensors. You will probably find that some sensors are marked as early or late production with no explanation of what that means, exactly. Spoiler: early production means 2001 models, and late production means 2001.5 models. If you're not sure which camp you're in, check the production date on your driver's side door jamb: dates 01/01/2000-08/31/2000 are 2001.0 model years; 09/01/2000-06/03/2001 are 2001.5 model years. The other time this date is significant is when you're shopping for ignition coils, but that's a different thread

Here's an example! Here's the connector used on the 2001 downstream right sensor



and 2001.5



Note the connector is completely different. They're even a different color.

You'll probably also find that there are also universal options available as well. I don't have any first-hand experience with them, but my understanding is they're sold without the connector, so you simply cut off the old sensor and tap into the existing wiring. My guess is all three options are exactly the same and the only difference is the connector they ship with and possibly the wire length.

I noticed that Denso doesn't seem to make the distinction between 01 and 01.5 so while they're a reputable company I wouldn't buy from them because there's no guarantee which connector you're getting. On that same note, don't trust a parts counter that doesn't ask which one you need. You're best off picking ahead of time and simply handing them the part number you need.

Good luck!

Thanks for the heads up. Do you know what o2 sensor is bank 1, sensor 2. I have both low voltage slow response and high voltage. P0139, P0138. No cat code yet.

Bank 1 is passenger's side, bank 2 driver's. Sensor 1 is upstream, sensor 2 downstream. Good luck with that one, I remember the wire being a tremendous pain to route up the firewall! I think I taped the connector to the end of a straightened coat hanger and fed it up that way. Good luck!

Just a warning regarding using the universal sensors:

I was unable to get the old wire sufficiently loose (passenger downstream sensor) to get it out of there and re-use the wire/connector. Obviously, they are anchored (plastic things sorta like cable ties) to the engine before the engine is put into the car, and I just couldn't get to them. So, I ended up buying the specific-fit one after all. You may or may not have better luck/skills/tools, but it also saved me from having to attach the old cable to the new one. Fortunately the good folks at autohausaz let met trade the universal one back in on the specific one, despite the usual industry policy of no returns on electrical items.

-Gary

Just changed Bank 1 Sensor 2 this weekend so I hopefully don't have the check engine light on anymore (its been on for a couple years). Removing the old sensor wasn't too bad but it took some effort and prodding to route the new sensor. The monitor for that system still hasn't registered as ready with my code scanner so I don't know for sure yet.

Since the OEM sensor is a Bosch, I thought I'd give a Bosch from autozone a try, the direct fit and not universal wires. This was $80 instead of $150 for OEM from courtesy parts.

Removal tips: The first two wire ties come loose easily with a flat head screwdriver. The third one (closest to the sensor) is really buried up in the engine. I managed to pop it free from below using a metal yard stick and a good strong push.

Installation tips. I used masking tape to tape the new connector to the old sensor and pulled the sensor/connector combo up from the top. This would be easier with two people but I managed to get it snaked through the engine bay after about 15 minutes of pushing and prodding. Its pretty tight back there. The two upper wire ties were fairly easy to snap into place but I didn't even try for the buried one. I just zip tied the wire to the transmission fluid dipstick tube and called it good.

As far as fit goes, the autozone direct fit sensor worked well. The wire ties lined up pretty good. We'll see how it does for longevity.

Nice write up! Just what I needed.

FYI I just passed emissions again with one monitor "not ready". Even though I replaced the sensor, I hadn't done the right kind of driving to set the monitor for this system.

If you have a downstream sensor that needs replacing and don't want to pay to replace it, most emissions tests will allow for vehicles (i think the model year is 2001 to 20??) to pass with one monitor reading "not ready". Before 2001 two monitors can be "not ready". The monitor for these sensors appears to be the last to set since it requires a few highway drive cycles, all of the others set after 1 25 min drive, half of it on the highway.

I have passed twice now doing this.

Update to the above post: The autozone bosch sensor has "set" its monitor so my pathfinder has a clean bill of health with no Check Engine Light for the time being.

I actually have an update of my own: I bought new upstream sensors for mine as well, and got the Bosch 13224 for the driver's side since it was specified by Bosch and every other parts store as being the replacement part. Like a fool I took their word for it and didn't compare to make sure. Long story short, it couldn't have been more wrong. The connector was completely different (I'm guessing the same as the 2001.0 uses), and the cable was only about 10 inches when it needed 2 feet. Even the wires were a much larger gauge than the old one! I ended up getting the 15363 instead, and it was a perfect fit. The peculiar thing is that 13224 is specified as the replacement for 15363, and as such, the 15363 isn't officially available any more. I was able to snag one of the few remaining off Amazon because none of the local parts stores couldn't source one.

I don't know what's going on here, but I'm pretty cranked about the whole thing and will be getting ahold of Bosch to request they get things straightened out. In the future, if you're in need of the 15363, I recommend getting NGK/NTK or some other brand instead, and make sure the pictured item reflects your setup.

On a related note, the 15343 was a perfect fit for the passenger side.

13224:


15363:

Lots of really good info in this thread thank you. I'm just curious where to buy from now...I've read that Advance Auto Parts is the best but i'm actually finding the same exact part numbers on Rock Auto's website for about $40 less per sensor which sounds good but the only thing that scares me is that's about the same price as the universal fit ones. But if the part numbers are the same they can't just lie can they? Any input would be appreciated as this will save me about $80 bucks, thank you.

I still have no issues with the Bosch I bought from autozone but it hasn't even been a year yet. It was a direct replacement with the correct connector, length, and spacing on the clips. I think it cost a few $ more than the universal but much cheaper than the OEM part# from courtesy parts.

first my stats: 02 QX4 190k second engine

Getting the codes for bank 2 sensor 2 O2 sensor fail (P00068 & P00156,I think). found Bosch part match on amazon for $70, will share if it fits and exact part number later. Spraying with PBlaster for a few days to loosen.

Two questions:
1). I'm up in CT and the pipe is pretty damn rusty, am I gonna have to use trickery to get the new sensor in? how do I avoid the socket falling away and leaving nothing to plug the new sensor into?

2). Where is the plug on the top side of the firewall?

Thanks for all the great posts here, best pathfinder slash QX4 forum out there!

relaxinrm wrote: ↑

Fri Oct 06, 2017 6:19 am

first my stats: 02 QX4 190k second engine

Getting the codes for bank 2 sensor 2 O2 sensor fail (P00068 & P00156,I think). found Bosch part match on amazon for $70, will share if it fits and exact part number later. Spraying with PBlaster for a few days to loosen.

Two questions:
1). I'm up in CT and the pipe is pretty damn rusty, am I gonna have to use trickery to get the new sensor in? how do I avoid the socket falling away and leaving nothing to plug the new sensor into?

2). Where is the plug on the top side of the firewall?

Thanks for all the great posts here, best pathfinder slash QX4 forum out there!

I don't know the answers to any of those questions, but wanting to replace mine I'm all ears for answers or your experience when you do.

relaxinrm wrote: ↑

Fri Oct 06, 2017 6:19 am

first my stats: 02 QX4 190k second engine

Getting the codes for bank 2 sensor 2 O2 sensor fail (P00068 & P00156,I think). found Bosch part match on amazon for $70, will share if it fits and exact part number later. Spraying with PBlaster for a few days to loosen.

Two questions:
1). I'm up in CT and the pipe is pretty damn rusty, am I gonna have to use trickery to get the new sensor in? how do I avoid the socket falling away and leaving nothing to plug the new sensor into?

2). Where is the plug on the top side of the firewall?

Thanks for all the great posts here, best pathfinder slash QX4 forum out there!

No idea bout number 1 besides hope and pray. Mine went just fine. As for question 2, get under the car and follow the routing with your eyes. The shielding should be color coded if you have OEM sensors in now. Popping the clips can be tricky and don't pull the wire for the old senor out without at least leaving a pull cord in its place. I just taped the old sensor to the new connector and pulled it through that way.

1. The bung on the header is welded in place so it shouldn't go anywhere once the sensor is out. If it does break off for some reason you'll need it to either be welded back in place or simply install a new exhaust pipe. Your best bet for minimizing the risk of it breaking off is soaking it in PB like you said, and heating up the exhaust pipe around the sensor with a torch. The less cranking you have to do on it, the better.

2. Both the upstream and downstream O2 sensors connect in the same general location. On the passenger side, it's under the engine cover in the very back. On the driver side, it's on the front of the engine to the right (if you're standing at the radiator) below the engine cover. The upstream one will be a light blue connector and the downstream will be dark green, if I'm remembering correctly.

If you have a ".5" model year, then always order parts for the next year up. The parts places don't know anything about the mid-year changes so skip all the hassle.

I have a 99.5 but I have to order parts for 00 for them to be correct.

alright 02 QX4 bank 2 sensor 2 replacement a success. Thanks to those that gave me tips!
Here's the highlights.
1. Bought the Bosch Original Equipment 13651 Oxygen Sensor $62 on amazon
2. hit that old sensor with pb blaster once or twice a day for a few days
3. cranked that old sensor off with some sweat and a lot of undercarriage rust falling on me
4. screwed the new one in the old bunghole carefully
5. unsnipped the old sensor from a wiring harness (noting location) then zip tied the new adapter to the old sensor.
6. went to the top of the engine and found the old adapter - it is up top a few inches to the driver-side and towards radiator from the engine's oil cap. this too was a stiff connection to break
7. pulled that old sensor and adapter up the firewall and took care to jimmy through and reposition the same way as the old one
8. went back down and zip tied the new sensor line to the wire harness so that the new sensor wire stays well clear of that hot-a** catalytic converter.

Thanks to this thread, I've just realized mine's a 2001.5, since my door jam reads Date: 12/00.

Cheers!

Hoping someone will see this. To confirm is upstream the 02 sensor under the front seats or around there front feet area and the downstream is the one towards the back of the car? Would appreciate the clarification.

Downstream is near your feet, very easily accessible from the bottom. The upstream sensors are further up the exhaust, near the middle of the firewall. They're right above the catalytic converters and much more of a pain to get to.

atraudes wrote: ↑

Mon Mar 30, 2020 5:08 pm

The upstream sensors are further up the exhaust, near the middle of the firewall. They're right above the catalytic converters and much more of a pain to get to.

Now that's an understatement. The drivers side is a PITA and the passenger side is damn near impossible. With the angle everything is at, and I've got all sorts of different sized extensions and U joint, I ended up bending the old O2 sensor taking it out. After having to hammer the socket on since the OE part has a little flange on it so the socket won't slide over it.

Thanks for the clarification guys.

One more quick question. So with a P0138 code. (Bank 1 sensor 2). I should first try and change out the 02 sensor. If that doesn't work and I have to replace the cat. That would be the front right that needs to be replaced right, not the rear right cat? Since the front cat would come before the sensor 2 correct? Example, I would need Davico part 18044? Really appreciate all the help. I just bought a stainless l shaped anti fouler and it seems to have made the issue worse than the cheap one from auto zone. It pops on almost every time now with a check engine light.