Ive read tons on this subject but not sure what to do. After initially throwing the code, I changed the air filter and cleaned with MAF with appropriate cleaner. Cleared SES light and thought problem was solved. After about a week, the light came back on, same code. Cleared code, week later light back on. I'm having absolutely no problems with the vehicle at all. Everything seems normal. Mileage MAY have dropped off a little bit. I don't want to start throwing parts at this thing without some kind of an indication of a problem, other than the SES light.
I know the maxima MAF is "cheap" but really don't want to do that until I have a better feel for whats going on.
Any ideas are welcomed. Thanks

'03 Pathy, 169,000 miles, 2WD

-fuel filter changed about a year ago

You do not notice any driveability issues because the rear oxygen sensor has taken over for the potentially failed upstream sensor.

Check for intake plumbing air leaks and try to verify fuel line pressure following the directions on page EC-64 of the FSM.

Since you reset the code once or twice, the sensor is probably bad though. This is a direct-fit replacement O2 sensor. I believe the OEM for the oxygen sensors on a 2003 Pathfinder is Bosch, but it might be NTK. Either way, the Bosch one should function fine.

Here is the location of the oxygen sensor and its harness connector:





You'll need a 22mm (preferable) or 7/8" oxygen sensor socket to replace it.

So you do not believe this to be a MAF issue?

I have this same thing posted on another Nissan site.

This is part of one of the replies I got:

"In my experience, a faulty MAF sensor tends to be the most common issue, especially if you are not experiencing a drivability issue, which would be more likely if you were have a low fuel or fuel pressure issue."

I really don't know. I've not done much DIY on this pathfinder. I've previous owned a jeep wrangler and did quite a bit of work on it.

P0174 is an upstream oxygen sensor code. Sure, the MAF can potentially be a cause as stated in the FSM, but if you're not encountering driveability issues (i.e. are in limp mode due to a failing MAF and can't go over 2,400 RPM), there is no fuel delivery issue and pressure is normal, and there are no intake air leaks, it's most likely going to be a faulty oxygen sensor, especially at 169,000 miles.

Makes sense. I really appreciate you help. I'll start pricing sensors.

Is this worth looking into?

http://shop.advanceautoparts.com/webapp ... GRPEMISAMS_____

Those can be hit or miss and completely depend on how well you make the connection. You cannot solder oxygen sensor wires because they "breathe" through the wires.

I replaced a rear O2 sensor with one from AAP. It was a Bosch OE-type direct fit sensor that I got for $50 after an AAP discount code. Apparently, AAP doesn't sell any direct-fit sensors for 2003 Pathfinders, which is why I linked to one on Amazon.