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  #1  
Old 10-10-2017, 03:54 PM
Bachida Bachida is offline
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Default 2009 sentra 0171 code

Hello and excuse my ignorance.
2009 Sentra with 87,000 miles.
I have received this 0171 code for awhile. I tried the simple things first like gas cap, clean the MAF sensor, fuel injector cleaner and air filter. Before I start spending non refundable money on electronics my son reminded me that a few months before this code popped up my oil fill cap came off. I have never added oil to this engine between oil changes. I don't change my oil. How this happened ????? Needless to say after driving on the turnpike oil was everywhere under the hood. I washed the engine down at the carwash. Could oil/engine cleaner have gotten into some of the sensor connectors that over time is creating a connection issue. I tried to find online a cable harness schematic that might show me the location of electrical connectors around the engine compartment but was unsuccessful. Am I wasting my time on this idea or should I start purchasing sensors and change them out.
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  #2  
Old 10-11-2017, 03:41 PM
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smj999smj smj999smj is offline
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Usually when water gets into a connector and creates an issue, it does it by shorting the circuits inside the connector or by corroding them and creating a high resistance or even an open circuit, all of which usually trigger a trouble code. So, unless you have stored trouble codes other than the P0171 code, I'd be doubtful. Of course, the only way to be sure would be to go through all of the engine compartment harness connectors, open them up and dry them out with electrical contact cleaner and compressed air.
If there are no vacuum leaks under the hood (split or loose fitting intake ducts, disconnected vacuum hoses, leaking intake manifold)...and the fuel pressure is within specs, which you will only know by checking it with a fuel pressure gauge...the most often culprit that'll cause a lean system code is a faulty mass air flow sensor (or, "MAS"). They usually fail and set MAS trouble codes, but not always and even trying to check them using a scan tool by viewing data logging can be tricky to confirm a faulty MAS. P0171 codes caused by bad oxygen sensors or air/fuel ratio sensors are often accompanied by a code for one of those sensors, as well. If it were me and I didn't have a scan tool nor wanted to go to a shop and have it properly diagnosed, I would start by confirming the fuel pressure is within specs and would then replace the MAS. That said, trying to fix a problem by going the "guess route" and just keep on replacing parts until the problem is solved can get expensive if one doesn't correct the problem with the first one or two parts...and sometimes a part isn't always the problem (circuit issues are always a possibility, like opens, shorts, high-resistance and poor grounds). The proper way to go about this would be to download the Engine Control chapter of this vehicles factory service manual (which might be available in the "knowledge base" section at this website) and follow the step-by-step diagnostics for DTC P0171.
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Old 10-11-2017, 04:58 PM
Bachida Bachida is offline
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Thank you for the very detailed reply. I have a code reader and it is always the 0171 code no others. The engine runs good although every once in a while when starting it idles rough for a second or two until i rev the engine once or twice the the idle is fine. I think I will try the fuel pressure first then the MAS sensor if pressure os good.
Thanks again for the reply
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  #4  
Old 10-16-2017, 04:19 PM
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smj999smj smj999smj is offline
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If you replace the MAS, stick with Hitachi or genuine Nissan for best results.
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  #5  
Old 10-19-2017, 03:48 AM
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mpe235 mpe235 is offline
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Inspect the intake hose from the air cleaner housing to the throttle body. Make sure there are no holes or cracks in the rubber.

Quote:
Originally Posted by Bachida View Post
Thank you for the very detailed reply. I have a code reader and it is always the 0171 code no others. The engine runs good although every once in a while when starting it idles rough for a second or two until i rev the engine once or twice the the idle is fine. I think I will try the fuel pressure first then the MAS sensor if pressure os good.
Thanks again for the reply
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  #6  
Old 11-07-2017, 07:28 AM
Bachida Bachida is offline
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Thanks you smj999smj for your help. Fuel pressure is good. All hoses and tubes good and crack free. I replaced the MAS sensor and that cleared the code. Before I continue I had in an eariler post my car has 80,000+ miles and I don't change my oil... I meant I don't change my oil myself. It gets changed every 3,500 to 4,500 miles by a service center. My problem now is starting and cold engine idle especially now that mornings are getting colder is very rough almost stalling. I have to be carefull when driving and coming to a stop sign or red light that it won't stall until it reachs operating temps. Again the 0171 code is gone. I have gone through the exercise of PIA process
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  #7  
Old 11-07-2017, 07:33 AM
Bachida Bachida is offline
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Sorry my fat thumb hot the submit reply button. I have gone through the PIA process of teaching the computer of the new MAS sensor. It took many tries to complete successfully. Once the process is completed sucessfully can it be repeated? I have tried many times with a stopwatch to do but I never was anle to get through it successfully.
Thanks again for helping me.
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  #8  
Old 11-07-2017, 01:51 PM
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bennyb53 bennyb53 is offline
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Quote:
Originally Posted by Bachida View Post
I have gone through the PIA process of teaching the computer of the new MAS sensor.
The MAS is Plug n Play. When engine reach normal operating temperature the computer starts receiving data. If engine don't idle correctly, do this:

Attention Required! | Cloudflare

If engine won't idle according to Specs you may need to do Idle Air Volume Learning procedures:

Attention Required! | Cloudflare

Two words you must pay attention. "at least" and "within". If instruction says at least 3 seconds, you can go 4 or 5 seconds with no harm. If it says "within 5 seconds, you must complete the operation without going over 5 seconds. Do Not Rush yoiu have plenty of time.
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  #9  
Old 11-07-2017, 03:48 PM
Bachida Bachida is offline
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Thanks bennyb53 I will do the recommended. From what I read in different posts is it may take 20+ miles for everything to settle out after performing procedures such as these.
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  #10  
Old 11-07-2017, 06:58 PM
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bennyb53 bennyb53 is offline
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Nope! When procedures are done correctly the ECM will respond instantaneously and you will notice the engine will idle normally within seconds.

When I do the IAVL I simply do this: Key to On for 3 seconds then Off 10 seconds 3x. After the 3rd 10 seconds Off, turn Key to On for 3 seconds then Perform #7. I noticed #7a should read: Depress and Release the gas pedal 5x within 5 seconds. In #8, the MIL will blink within 10-12 seconds. When MIL stop blinking, release the gas pedal within 3 seconds. good luck.
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