So SES came on my Pathfinder came on couple of weeks ago. I tried closing the gas cap little tighter just in case After few drives, the light went out for couple of drives then SES came back on.
I begin to wonder if running gas close to empty on few occasions may have caused it but light never went out after couple of fill ups and few trips.
Finally, I rushed to Autozone to get code read. P0171. System Too Lean (Bank 1). The guy said something like it could be fuel injector or many other things. Better take it to a shop, he said.
So I didn't. I am going to try to figure out what the problem is before I let the dealer rob me.
It's probably not gas cap but I think I'll go out and get a new one since it's only few bucks.
From what I gather, it looks like it's MAF in many cases with P0171 for Pathfinder.
I bought a modest scanner, Actron P9175. To save on trips to Autozone and to see if I can get any additional info... (and because my wife let me...)
I/M Monitors (Emissions Systems) monitor on the scanner all returned ok... So I guess that means all the monitors are working alright.
Looked at Freeze Data when P0171 triggered.
Engine RPM : 2312
Coolant Temp: 192 F
Short Term Fuel Trim1 : -4.6%
Long Term Fuel Trim1 : 32.0%
Short Term Fuel Trim2 : 2.3%
Long Term Fuel Trim2 : 30.4%
Short Term Fuel Trim3 : -100.6%
Long Term Fuel Trim3 : -100.6%
Short Term Fuel Trim4 : -100.6%
Long Term Fuel Trim 4 : -100.6%
Vehicle Speed : 64 mph
Fuel System 1 : CLSD
Fuel System 2 : CLSD
If anyone notice anything interesting in above Freeze Data, any input would be appreciated.
I got a MAF contact cleaner. I think you can get similar sensitive electronics component cleaner from Radio Shack. I cleared the SES but haven't had time to try cleaning MAF yet. I will report back as to my success or failure.
I just want to log my problem here for others with same problem.
The cleaning was pretty easy. You need Torx T20 security bit. They try their best to make sure simple things are unnecessarily hard for DIY people. I had regular Torx bit but not security bit so I had to run to Sears to pick one up. ($9.99 for 6 assorted torx security bits)
1) Locate the MAF sensor. Find air filter casing. Follow it back to the engine. It's close to the air filter casing. It's hard to miss. I am only taking out the sensor instead of the whole MAF casing.
2) Take off wiring harness.
3) Take off couple of screws using torx T20 security bit.
4) Pull out the sensor. It take little bit of force and wiggling.
5) Spray the cleaner on to two areas that I can see shiny metal. Give it a good spray bath.
6) Let it air dry.
7) Replace the sensor.
8) Spray the cleaner on the wiring contacts.
9) Let them dry.
10) Plug the wire.
Let's hope this works out. I erased the codes using my OBDII scanner. Unlike O2 sensors, I believe MAF do not require any additional clearing steps.
I will report back in couple of days and announce if SES light comes back on or not. I have to replace tires on this Pathfinder so I am hoping to avoid any extra cost of MAF replacement or other services.
It's been two days. I made several errands on this car. I did not drive for a extended distances (no more than 5 miles at a time). SES light is still off. The car seems to respond better with gas pedal but it could just be my mind playing with me.
Many people claim better gas mileage and performance after cleaning MAF...
I'll report back if SES light comes back on with same code but so far so good.
Well, SES came back on tonight. What I found interesting is the freeze frame information which seems similar with the information I got initially. Same speed and RPM which is very curious. The light didn't come on when I was driving around town. After couple highway trips SES came back on.
Engine RPM : 2312
Load Value : 46.2%
Coolant Temp: 190 F
Short Term Fuel Trim1 : 7.0%
Long Term Fuel Trim1 : 32.8%
Short Term Fuel Trim2 : -4.6%
Long Term Fuel Trim2 : 30.4%
Short Term Fuel Trim3 : -100.6%
Long Term Fuel Trim3 : -100.6%
Short Term Fuel Trim4 : -100.6%
Long Term Fuel Trim 4 : -100.6%
Vehicle Speed : 64 mph
Fuel System 1 : CLSD
Fuel System 2 : CLSD
I am not sure what this means now. Car drives fine.
Any one have any additional thoughts? Maybe cleaning wasn't good enough and MAF has gone bad?
On unrelated note, the steering wheel used to shake quite a bit 55-65mph. I had the tires balanced at a shop that had Hunter GSP9700 with road force as suggested by another post on this forum. Shaking is gone.
I think I may have found the problem with my pathfinder. I should've checked this first I guess. While I was changing oil on the Pathfinder, I pushed on the duct that leads to engine block unintentionally.
It moved more than I anticipated. I checked the hose-clamp where it makes connection to engine block. What do I notice? Very lose clamp. I tightented the clamp.
Hi there,
Im having pproblems with my 2001 Pathfinder LE. For a month now ive been getting P0171 and p0174 error codes. The manufacturer service tech manual states the following as the possible causes in this order:
Air Intake Leaks
Front o2 sensor
Injectors
Exhaust gas leaks
Incorrect fuel pressure
Lack of fuel
MAF sensor
Have not taken it to the dealer yet because this is a non specific code and I dont have very much faith in them. However the driveability of the vehicle has been affected. It hesitates, lurches and loses power especially when accelerating. I have cleaned and monitored the output of the maf sensor during operation and the output seems to be well within spec. Have also scoped both front o2s and found the right bank slow in responding at times. Replaced it. Same problem. Replaced air filter, fuel filter and visually checked for air intake leaks. Nothing obvious. Next thing I guess would be to have injectors cleaned, monitor fuel pressure, and possibly have the air sytem smoked out for leaks.
The problem with this code that it does not point to a hard fault on any one device. Anyway any help out there would be helpful and I will also report back any findings as this could be a common problem.
Have you checked all your vacuum line? What about your air filter? It would seem you might have some type of air flow problem....these are the 2 cheapest fixes the next would be the air flow meter which can be costly 150 or more
I drove this car for a year without much problem with P0171 code on. However, IL requires emissions test so I had to fix it. I finally gave in and took it to a mechanic. I didn't want to take a chance with replacing MAF sensor myself since part cost $500 since I wasn't sure it was the problem 100%.
The mechanic first suggested cleaning MAF sensor. I told him I already try it. So he ran a vacuum seal test with colored smoke. He didn't find any problems. He then looked at the diagnostic data and noticed the trim figures were way too high. He said under normal driving conditions it should be generally at 5% at most but he was seeing 30%. To make long story short, in this case MAF sensor is bad causing fuel trims to go little crazy.
With labor, tax, and $500 MAF sensor part, I paid $700. The light is off now and it hasn't come back for a week. He basically charged me MSRP for OEM MAF sensor which he had to get it from a Nissan dealer. You can probably find it few bucks cheaper if you did it yourself.
Last edited by slacker01 : Sep 21st, 2007 at 02:01 AM.
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