MattBeaty

A few weeks ago my 2K Maxima's SES light came on. My dad and I hooked up our OBDII Scanner and it said the code was P0171. We assumed that it was one of the oxygen sensors, so have not done anything about it yet. Now after hooking up the scanner again, it has also thrown the P0174 code. The car is running fine still, and the oxygen sensors are giving and output. Both of the codes deal with the two banks of the engine running to lean. After reading some other threads I think my symptoms look like the beginning of a MAF failure. Is there anyway to determine if this is the problem, or do I need tho check other things, such as the fuel pump, filter and Injectors.

MattBeaty

Here is a little more information to add to the problem. We cleared the codes a few weeks ago, it has taken them about 60-70 miles to come back on, so whatever the problem is, it is sporadic when the fault occurs. Before the codes came back on, we hooked it up to a OBDII scanner again. I was able to check the values that the MAF was reading. When the engine was cold, at idle it was reading .6 lb/min after the engine warmed up, it lowered to just under .3 lb/min. The values seemed to be stable and did not jump around very much. When a MAF is failing, is it possible for it to be functioning, but not consistently, or does it go from working fine to suddenly dying?

Menasor

iTrader: (2)

Did you check fuel trim? I beleive the DTCs you got are lean codes for bank one and bank two. Keep in mind that MAF sensors are a common problem on 5th gens more so on 3.5VQs. You can get one from DAVEB at Southpoint Nissan for 80 dollars plus shipping. There are tons of threads about this subject as to the symptoms of a bad MAF. Even if you aren't experiencing driveability problems now you might later. But if you are able to check fuel trim then post what your readings are. Hope this helps a little.

MattBeaty

If I remember correctly, the long term fuel trim was right around -30 and the short term was -3.

Menasor

iTrader: (2)

Do you have access to a scantool. I take it you do. First thing to check for are air intake leaks after the Maf sensor. Make sure the clamps on the boot are tight. Make sure the boot is not torn. That goes for the hoses coming off the boot as well. Check for exhaust leaks before the main catalytic convertor.Check the O2 sensors, warm-up the car to operating temperature and see if the front o2s are switching from rich to lean constantly. Rev the engine to about 2000-25000 rmps and hold it long enough to see the o2s swithching from rich to lean rapidly. Check fuel pressure. At idle with the fuel pressure regulator hose connected, your looking for 34 psi. And when its disconnected, it should read 43 psi. From the looks of things it looks like a MAF problem. Do you have any mods...like an Intake? Oh one more thing is that a minus 30% reading you got for long term fuel trim? Or does it just say "long term fuel trim- 30% or long term fuel trim -30%" At the moment it looks like your car is running rich and not lean. Its taking away fuel if I am interpreting your data correctly. Even then 30% is high. Your call man, if I were you I would be calling DAVEB for a MAF sensor. Have you ever had to replaced your MAF sensor before? I was looking at your second post and the readings for the MAF don't look right. At idle your looking for 2-6 gm/sec and at 2500 rpms your looking for 7-20 gm/sec. Sorry for the long post, hopefully you'll find something usefull that will help fix your problem. Let me know if you need any help. I'll try my best. Take care.

MattBeaty

Thanks a bunch for the advice Menasor. My car does not have any engine mods and I am still running the stock MAF (61000 Miles). The O2 sensors are switching just like they should (One of them was replaced about a year ago), so I think that most likely you have hit the nail on the head with your diagnosis, thanks again.

Menasor

iTrader: (2)

No problem. There was this time, I got an 04 Sienna in for the same codes, it was a leak in this valve on the side of the intake manifold. I spray brake cleaner in the side of it and watch fuel trim change change. So I had to replaced the valve. There was a TSB for it and was following the diagnostic procedure. Reason I asked about mods was because oil base air filters, such as the ones on most intakes, oil up the hot wire on the MAf and skews the signal to the ECM. But you might know that already. Anyways on some MAFs, you can actually clean them with electrical contact cleaner, but I don't know about our cars. I have cleaned my Maf before but don't know if I am actually making it worse. Anyways if you know who DAVEB is, I suggest you get the MAF sensor from him. Dealers around here charge 400 dollars for the MAF. Might be the same with dealers around your area. Let me know how it works out for you. Take care.

YuAnChen

iTrader: (1)

Got same code
SO is it maf ?

Menasor

iTrader: (2)

Could be. I posted some things that you should check for. It's hard for me to tell you that it's the MAF since I am not there to look at your car. Good luck. If you need help, I'll try my best to supply as much info as I can.

nismo_star

iTrader: (8)

Its a MAF

If you get Nissan MAF ending in -AD200, which is countermeasure MAF for 00 Maximas, you will need updated reprogramming from the dealership otherwise you will get P0100 codes coming up.

xiaozhu

Before replacing MAF, SES P0171. Engine stalls after cold start.

After replacing MAF, SES P0140. Engine stalls at traffic lights, especially after warm start. I believe the MAF is an aftermarket AD200.

Would the updated reprogramming from the dealership resolve the problem?

JeffroBodine

MAF part# 22680-2Y001 from courtesyparts.com $89.90 will solve your woes. It worked for me.

Wjb727

At 81,500 miles, my 2000 Maxima just posted a PO171 code _ Bank 1 system too lean. I've just read through your thread and was wondering if this is simply an oxygen sensor problem or something starting to go worse?
If it is just an O2 sensor, where is it located and would it be easy enough for a slightly mechanically inclined person to change it out?
If it makes a difference my car was set for California standards. I have seen problems with parts that mess up California made cars.

Wjb727

The rascally car just decided to turn its SES light off by itself (PO171 code). Of course, that happened right after I bought MAF cleaner and throttle body cleaner and threatened the car with personal maintenance. I'll still clean the sensors since I have the cleaners. It doesn't look that difficult, even with my old hands.
Would this be sporadic in nature with a dirty Mass Airflow Sensor?

maxiiiboy

The fact that the light went off means that your problem is intermittent. However, it will likely become permanent in the future. Page EC-340 of the FSM lists seven possible causes that can trigger P0171:

• Intake air leaks
• Front heated oxygen sensor
• Injectors
• Exhaust gas leaks
• Incorrect fuel pressure
• Lack of fuel
• Mass air flow sensor

Without special tools that only Nissan dealers have, it's pretty hard to determine which one of the seven problems is yours. However, the first three bullets are common problems and reasonably easy to deal with: Check for leaks, use an additive (e.g. Seafoam) to clean your injectors, and if your MAF is OK, consider replacing your front O2 sensor (see the earlier post above). Re. sensor location - just search; there are good pictures posted on this forum. Also, get yourself a copy of the FSM; download it from here: http://boredmder.com/FSMs/Nissan/Maxima/