Just turned 100,000 last week and what do you know....I know everyone is sick of hearing about codes and I searched for several hours and want everyones thoughts. I have two codes for my 01 max from autozone P0171 and P0325. I am guessing the 171 is probably the maf. Everywhere I read 90% of the time this code means the maf is going or the AFM. What is the AFM????? I have the stock airbox with Irish44's drilled holes suggestion on top for better airflow. I have no performance issues over all the rpms but the car feels slightly sluggish to me. I think I am going to order a new one from Dave B. and install it myself. The other code of P0325 I am guessing is related to my fuel cap, fuel filler neck or O2 sensor. I have been getting a fuel smell constantly for a week outside the car and purchased a new gas cap from nissan for ten dollars and my stealership. I sanded down the rim for the rust,and am touching it up with black paint(per the nissan tech). After replacing the maf sometime next week when I get it and also the fuel cap I am hoping the issues go away. My next step will probably be to start replacing 02 sensors.......I will keep everyone posted on the progress of my dilemma...

 

AFM = air fuel mixture?

and yes, 171 is most likely MAF, and yes, MAF is directly related to the A/F (afm)

I had 171/170 on a ford and it was the oil from the K&N filter. I personally dont mod air intakes because of past issues.

 

Spoke with Dave B. today and ordered my new maf..He said the P0325 is probably a "phantom" code brought on by the P0371 maf code...I am hoping the codes go away but it might ultimately be a knock sensor with P0325..He quoted a price of around $150 and suggested I have a mechanic replace the sensor if the maf doesn't fix the problem..Has anyone replaced a knock sensor before???

 

Damn that sucks. But congrats on the milestone. Tim just reached it the other week too.
Give me a call this weekend if you need some help.

 

I too have to replace my MAF this weekend (luckly my mom works for Nissan) and I believe it is because of the modification of the airbox. I did the ghetto airbox mod, but since the SES light and problem diagnosis I have it back to stock and keeping it that way. good luck

 

afm=maf air flow meter

 

You MUST get your ECU reprogrammed after you replace the MAF. If you don't the car will run rich, big time. I just went through that whole mess. The dealer will charge about an hour's time to do the re-program.

Take a look at this thread for more details.
http://forums.maxima.org/showthread.php?t=538422

 

i replaced my maf back in the day on my 01 and the reprogram is not a must. you can do it if you want however. i had a before and after dyno with almost identical a/f ratio. there are also several other members that replaced the maf without the reprogram with no issues. i also had a wideband o2 monitoring the a/f during driving conditions and it also did not change.

 

the MAF went bad because it was time for it to go bad...your GAB didnt do it

 

I got my maf from Dave B yesterday and respect yours and Irishs' opinions on this site..Is it really necessary to pay 100 to the stealership to program the ECU like Tony W said a few posts ago???? I am replacing it with 00maxse in the next few days...I think I will see if the car runs "rich" after I replace it and go from there...Also I checked the stealership to make me laugh and they wanted a price of $480 for the new maf and install...PRICELESS.....and rewarding to do the job yourself..............

 

i dont think you need the reflash...the ECU should figure it out

 

Thanks sooner...I will see if the max figures out the new maf before I give the stealership any money...Will keep you posted after the replacement...Paul

 

DaveB FTW!

 

The ECU reprogram is not NECESSARY but doesn't hurt. My MAF went at about 45K and the car ran the same after the replacement.

I only got the ECU reprogrammed at ~65K miles when my car threw a P0420 code.

 

I just wanted to touch base on a subject in this thread again....

I have an '01 SE with about 128K. I've replaced all of the catalytic converters, because of 2 codes that have came up. My question is this....

Is the stealership 'reflash' that much necessary? I think it's just them plugging in their $5000 SnapOn Modis computer and getting a diagnosis/code erasing from it.

My only problem is that I'm due on inspection, and you need to drive the car at least 50 miles without a check engine light on before you can get it inspected. What are the chances of the light coming back on later on if you don't get the ECU 'reflashed?'

 

Check the Nissan service bulletins that talk about replacing the MAF. I confirmed this with two different Nissan techs (who were NOT trying to sell me stuff).

You DO need to confirm the ECU has the right part number (it's what Nissan uses for software versions). If it doesn't have the latest number/version you DO need to re-flash or the car will run very rich.

If you want to try and see what happens, keep track of your mileage before and after the AFM replacement. If your mileage drops significantly (mine dropped 5 MPG), then you need the re-flash. If everything is as it was, then maybe not. As I said in my other post, the dealer said my ECU was up to date, but when I brought the car back two tanks of gas later because of the terrible mileage, they "found" the ECU was WAY out of date. After re-flash, so far so good.

 

the car is going to run stoich at or very close to 14.7 in partial throttle driving. the a/f is also determined by the maf and primary o2 sensors at partial throttle. only at WOT does the maf take over and solely determine the a/f. if the new maf did change the a/f then you would have to drive WOT to notice a mpg drop.

 

That's not what I experienced. I drive 100 miles a day on the freeway (70 MPH) and I noticed the big drop.

The "old" ECU software version with the old AFM got me 25-26 MPG on the freeway.
The new AFM with the "old" ECU software got me 20 MPG.
When they re-flashed the ECU to the latest software, I got my 25-26 MPG back.