so my parents 00 Max has been getting some pretty crappy gas mileage recently. About 200-210 on a tank. 50/50 freeway/city driving. Seemed like it was getting a bit slugish but wasnt sure. Yesterday i got code P0138. My scanner says bank 1 sensor 2. Can someone tell me which O2 that is so i dont have to figure it out myself?? heheh thanks!

 

The location depends on if the 2000 is CALI or FED spec. And since you're in CA, I assume that you're supposed to have a CALI spec for smog purposes. In that case, the sensor is the one on the front of the y-pipe.



See here for more details:

http://maxima.theowensfamily.com/tsb/NTB02-051a.pdf

 

You're lucky. That one is easy to get to. 15 minute job.

 

the only thing i am wondering is that secondary o2 sensors are used to monitor only and have no ability to alter a/f. a bad secondary should have no effect on a/f therefore no change in mileage. i had one bad secondary o2 sensor and the other was disconnected after my header install for a few weeks with no change in gas mileage.

 

Good point, I completely overlooked that. IIRC, the only way the secondaries can be used to influence AF is if the primaries were shot too. Is that a possibility here?

 

i have heard of them assisting only in the situation you mentioned. i would just assume though that if a primary was dead then the code would have been pulled. i would also assume the secondary would only step in if the primary was dead and not just on its way out.

 

You should have codes then if you removed your secondary, irregardless of your current code.