‘02 QX4 - P0138 and P0328 on a 3000 mile road trip. Help me please!

[brickbox]

Folks, I am about 800 miles away from completing my 3,000 mile trip. Which also means that I need my R50 to run another 800 miles before I get home.

Today morning, while going to a sunrise hiking trail, the SES light popped on going about 75mph on the freeway.

Code reader shows P0138 and P0328.
I read some of the old threads here (as well as I could on my phone...) and it looks like changing the post cast O2 sensor is the way to go.

Can this be done once I get home? There will be about 90% freeway commute on the way back.

Nissan/OEM part is the way to go?

Any tips/tricks/write ups that you could share with me would be appreciated.

Thanks!

[Mike W.]

I'm seeing P0138 as a O2 circuit high voltage and P0328 as knock sensor 1 high output. Last year on vacation I had P0430 Catalyst System Efficiency Below Threshold (Bank 2) pop up after a steep off road climb but it went off eventually. With the knock sensor code you have I'd start putting premium in if you haven't already. Rule of thumb is as long as the Check Engine light isn't flashing it's not a big deal to continue driving it.

O2 sensors are semi generic except for the plug so any name brand such as Bosch or NTK/NGK will be fine. I put Ford fitment (but Bosch brand) in my QX4 and saw no codes on my 4K vacation in July.

[Rockwood]

I would just add to Mikes answer that one of the causes listed for the 138 code is a vacuum leak. Vacuum leaks can also cause knocking or the 328 code, so maybe look around and see if you can find a loose hose. That is bank 1, so passenger side of the engine. Might get lucky!

[brickbox]

I completed the trip back home yesterday without any issues. I erased the code and it never came back on. Car runs fine without any issues.
Should I consider changing the O2 sensor preemptively or just wait it out for now?

The only thing I did differently was to use generic "Sheetz" gas during that one fuel up instead of the usual BP/Speedway/Costco.

I'll take the engine cover off this weekend and try to see if I can find any cracked/loose vacuum hoses.

[Mike W.]

If I did one, I'd do both. But it kind of sounds like it's reporting correctly, but something is going on to cause odd readings. I think the rear sensors are the same so you might swap them and see if the problem follows the sensor or stays at the location it's at. Rears aren't bad to get to but I would never suggest that with the fronts which are such a PITA to get to, on them I'd just replace them with new if I was trying to check.

[brickbox]

Sounds good. I plan on monitoring it over a few more days to see if the SES light comes back on. If not, I'll leave it for now.
I crawled underneath and I don't think either of those O2 sensors are going to come out easily. So if I get the light back on, I might just end up changing them both as you recommended.