P0171 - Fuel Injection System Too Lean (Bank 1)

the light came on at 90K miles.

 

MAF perhaps.

 

check for exhaust leaks. listen for a leak before the cat.
then listen for air intake leaks after the maf.
if that's not the problem, you could check your front heated o2 sensor circuit.
it could also be the fuel pump, fuel pressure regulator, fuel lines, or the fuel filter. it could also be the injectors.

oh, and yeah, it could also be the MAF.

 

If you are also experiencing a rough idle and hesitation for the first minute or two after cold starting the engine, its the MAF.

 

lol, well id say its probably NOT the MAF, since that would throw a 0174 also...


could be one of several things, youll need to check the fuel trims and see when its lean (at idle, under accel, during cruise, etc.) and then go from there.

could be one of several things but its only affecting the one bank, or at least enough to set the code for that bank.

and jjames, thats the rear bank

 

hey, i'm just telling him what the troubleshooting procedure for a P0171 is.

 

yea but you said the 'front' HO2S. bank one is in the rear, IIRC

either way... you put him on the right track.
you find anything yet, tbone?

 

not yet, I am replacing the MAF when it arrives (tomorrow).

 

was bank 2 lean also?

 

How's it doing now Ryan?

Install took us all of 5 minutes.....

 

you might have a plugged fuel injector....can you hook it up to a machine and check the HC and CO readings? that would help out a **** load.
could it be a vacuum leak plugged fuel filter?

 

if bank 2 was lean then it would have throw this code PO174

 

I had the same exact problem when I hit the 85k marker. My cars threw a P0171. So I changed the MAF and problem solved. I had some hesitation accelerating, rough idle in the morning, and that damn SES light on. I swiched the MAF and everything went away. I'm telling you because I had the same exact code thrown at me and I the code pulled twice and they both were the same.

Good luck and its definelty the MAF

 

yes, im well aware of that, as i posted it earlier in the thread.


a MAF would cause both banks to go lean. due to variations in fuel trim, it could throw a code only for one bank, or maybe it just hasnt gotten that bad yet, but usually its both banks. either way, the fuel trims should be checked first.

 

When I had the CEL on I got a P0171, and only that code. Car ran great after I replace the MAF. You think that it would make sense that if the ECM detected one bank that is running lean to wait until the other bank starts running lean to trip a code? When I need to check fuel trim, it gives me the short term and long term values, obviously you already know that, what I am trying to say is that I have yet to use a scanner that tells me when the ECM is taking away or adding more fuel during idle, accleration, or cruise. I like to know what scanner allows you to see fuel trim under these conditions. T-bone do you have any drivability issues. I'm confident once you replace the MAF, your car trouble will be gone.

 

any generic OBDII scanner should be able to. a 'code reader' is a different animal. are you getting other engine data, like eng speed, ECT, etc.? usually autozone only has a code reader and thats all you get. if youre getting other data, usually trims will be displayed as 'LTFT1, LTFT2, STFT1, STFT2', etc. some cars are a bit more diguised in their names, GM for one calling them 'block learn' and 'integrator' and using numbers other than percentage figures for each.

 

100% air flow meter,

 

youre a better man than i am ^^^

 

I've been wondering how do you go about having a govern takin off or bypassing its functions. Because, it shuting down the engine really isn't what i need. A friend of mine told me that you wouldn't be able to find a computer that didn't come with one on it but i was wondering if there was a way to manipulate it.

 

govern? you talking about the engine speed limiter? why would you wnat to take that off?

 

Use an Apex i RSM (Rev Speed Meter)

Ask for it by name.

 

since menasor got his pee pee twisted about me not answering this question, thinking it was rhetorical... here goes.

it makes sense that the ECM would set a code when the fuel trim reaches the pre-programmed threshold for lean or rich. since a MAF measures the air intake for the ENTIRE engine, and since the air should be distributed evenly to all cylinders, a lean reading on one bank would mean the other bank is lean too. so now that oyu know this... HOW DOES A FAILED MAF SENSOR COMMAND ALL THE FUEL TO GO TO ONE BANK AND NOT THE OTHER?, meaning one bank it at stoich and the other is lean enough to throw a lean code.

a failed maf CAN cause a light for one bank only, but the trims will be borderline for the 'good' bank.

basically if the threshold is 25% well see:

STFT1: 1%
STFT2: 0%
LTFT1: 26%
LTFT2: 24%

both banks are lean, but 2 hasnt passed the threshold yet, so we only get the 0171 and not the 0174

so to answer your question, either bank can run lean without tripping a code, which is why the trims should be checked.

simple, really.

 

Great! After disconnecting the battery overnight, the light reamained off for about 20 miles. Then it came back on for <80 miles. Now the light is off (300 miles) and the engine is running much smoother than before the MAF replacement. Fuel economy is up as well.

 

The light is back on!

 

lol, pull the code...

funny how everyone was soooo sure it was the maf. there are other test to be done.

pull the code and get back with us.

 

ehhh... Im pulling the system too lean... but I have an Exhaust leak 100% Everyone thinks I have a crazy exhaust haha. an exhaust leak can cause the code? also when I start it up and dont allow it to warm up (might be normal) it like almost stalls if i start driving.

 

yep, same for me, I got the p0171 and p0174 codes a few weeks back, replaced both front 02 sensors and cleared the light, ran fine for a couple days and the light came back on day before yesterday, pulled code and it was p0171. Had autozone clear the code and I'm gonna see if maybe it will pull both codes next time..... I'm not sure what to check next, or how to check the trims, any ideas?

 

wondering if you got your car fixed T-bone? if so, what was it?

 

I had the p0171 and p0172 codes sometime back and replaced the MAF myself. The MAF came with a note that the ECM should to be updated but I didn't do it since I had read of others not needing it.

About a week later the check engine light came back on and the codes are

P0138 - Heated Oxygen Sensor 2 Circuit High Voltage (Bank 1)
P0139 - Heated Oxygen Sensor 2 Circuit Slow Response (Bank 1)

Could this be due to the ECM not been updated? Should I update the ECM or change the o2 sensor?

The autozone person when checking the codes took out the check engine light and it hasn't come back since the last couple of days.

Thanks

 

Any resolution to this yet???

 

I am also wondering if anyone ever figured out this problem. I am helping a friend of mine with his maxima and he is throwing this code. He told me the car is running fine but his gas mileage is down. He is throwing the P0171 "System too Lean (Bank 1)" code.

 

I have a 2000 Maxima GLE, 110k miles. At about 90k I had pinging even w/ premium gas, research here told me to replace the coils. A few hundred bucks to Dave B at Courtesy later and that problem was fixed.

Now it's at 110k and I've been having similar problems -- some pinging under moderate load, poor idle/surging on cold starts, and generally sluggish performance. A few weeks in to this the SES light turned on. I bought a Scantool.net Elmscan USB ODB-II scanner, and I found that the code was P0171. (Note to users of these tools -- you have to select only the values that the max. supports or else it will stop talking to you and you have to re-connect. Search around on the scantool.net forums for the list or experiment to find out which ones your car supports.)

The scanner told me that the MAF was still somewhat working, but the values didn't change much (0.4 to 0.8 lb/min? over full rpm range, seemed low) so I bought a new one and an OEM air filter from Dave B at Courtesy (1-888-254-6060); ~$101 to my door. In the meantime I tried to clean the MAF (not disassemble) and that completely broke it so the car was undrivable. The symptom was that the car would always throw P0171 and would never get any values from the MAF. The new MAF came today, so I vacuumed everything nicely and installed it, and I have a *whole new car*.

I need an oil change right now anyways, so unless someone here tries to talk me out of it I'm going to use their coupon and see if I can't negotiate a decent deal for an ECM software upgrade.

Thanks maxima.org!

-Peter,
Melbourne, FL
pic of my car: http://www-gt.diff.net/media/2005_04...e/img_0194.htm

 

I had the same problem. I had codes P0171 and P0174. I new it was the Maf, so for a year and a half I drove it anyway, just constantly checking the car for any new codes.
The car finally got worse last month, so I brought it to the dealer to replace the Maf. I heard the new MAf requires the ECU to be reprogrammed, so thats why I brought it to the dealer. A week after getting the new MAF, i get two new error codes, P0138 and P0139. high and low voltage for O2 sensor. Did the dealer forget to reprogram the ECU ? Has anyone else had this problem ?

on an unrelated note, if anyone needs a cheap OBDII tool, check out http://www.obddiagnostics.com/ If you have a laptop this is one little tool that you will use over and over.

 

P0400 - EGR Function (Close)
P0175 - Fuel Injection System Too Rich (Bank 2)


I'm getting these two codes on my 2000 SE. I'm beleiving the 400 code is that the EGR port is clogged and needs to be cleaned but the 175 is that MAF related?

 

FYI Yes I did a search guys!

Please help!!

Hi,

I was wondering what the end result was with the CEL codes of P0171 and P0174?

I am currently getting codes and symtoms. Car hesitated on accelerating after a cold start. My buddy cleared the codes in the parking lot just now. We restarted it and the codes didnt come back.. hopefully they dont come back on the way home. I've been reading up on this topic and I see that most people had to change coil packs and/or MAF.

Specs: 2000 Maxima V6 Auto, 67000km

Any help is appreciated,

Thanks

 

2001, 95K miles

I too am getting a P0171 code. Car is running fine except for a very slight hesitation for the first minute after a cold start. Recently started getting even more milage than ever (car has gotten apx 360 miles per tank for the last 6 years... now it's getting about 420 miles per tank). Maybe I shouldn't complain, but I know mixture that's too lean can damage the engine.

Here's the information thus far:

Short Term Trims B1 & B2 go up to apx +/-15% while driving.. they sit at apx +/-5% while idling in neutral

Long Term Trims B1 & B2 are fairly seady at apx +33%

MAF reads apx 2.5 gm/s at idle (600 RPM) and apx 8 gm/s at 2500 RPM

MAF goes up to 20 - 30 gm/s when at acclerating at highway speeds

I plotted MAF against engine RPM... they tracked pretty closely

Ran a can of fuel injector cleaner through the gas tank

Cleanned MAF sensor with MAF cleaner (didn't do anything)

Replaced B1S1 O2 sensor (didn't do anything)

Check vacuum at fuel pressure regulator (18")

No detectable vacuum or exhaust leaks

What is causing the trims to be so high? Does anyone have the ability to monitor their MAF reading while idling and under load.. I'm thinking the MAF is just reading somewhat low when under load causing the system to run lean...

Any suggestions?

 

my friend that had this problem fixed it by changing the MAF. Not sure if this is your problem but it was his. If you live close to some other .orgers you may want to see if you could meet up with one of them and try a different maf.

 

The problem was my MAF. The dealer wanted to charge me $645 plus install to change my MAF, im like no Thank you. So I then ordered one from Nissan (In Texas) online and I paid $109US for the same exact make and model that was in my car when I bought it from Nissan. It took my friend 10 mins to change it and it only cost me $109 for the MAF and a beer for my good friend that changed it for me.

Now in that being said, about a week after or so, I am getting a engine light check and I did a read with my reader and I am getting the following two codes.

p0139 --> 02 sensors Circuit Slow Response (Bank 1 Sensor 2)
p0138 --> 02 Sensor High Voltage (Bank 1 Sensor 2)

I called Nissan and told them that I am getting the following two codes after I changed my MAF. They told me did I reprogram my ECM? I replied no, does it need to be reprogrammed? He told me once you change the MAF you will need to reprogram the ecm for it to know that there is a new MAF etc..

Is this true? Is there another way to reprogram it by purchasing tools/software etc, that saves me not going to the dealership and paying 80+ for a 2 minute job of reprogramming my ecm... Would disconnecting my battery for 30 minutes, would that reset everything.........


Please let me know
Thanks in advance

 

I ordered the MAF sensor today. I tried two other things before deciding to try the MAF. #1 I measured the MAF reading from a similar Nissan engine... the readings were 2 to 3 times higher than mine, and the engine trims on that car were normal. #2 I checked for an intake leak by covering the intake with plastic wrap... the engine died moments later, however, the vacuum stayed until I pulled off the plastic... you could hear the hiss when I pulled it away.

I'll let you know if it solves the problem.

 

I have a 4th gen with the 00VI swap and after the swap i had got the same code.

Turned out for me it was the fuel pressure regulator that came with my 5th gen 00VI.. it made me run lean at idle and when i swapped it i noticed there was a kink in the FPR where it got bent somehow.

Anyways swapped the FPR and problem solved.

Check out the Fuel Pressure Regulator it could be it that's giving you that problem