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p-0171 keeps coming back

I did a lot of research on the code and learned a lot about it.

First.. the sensor is sensing the exhaust and reporting it to the pcm, just like it does all exhaust levels. The pcm then interprets this and fuels based on the info. When certain thresholds are met the pcm is programmed to report back to us via the code/SES light. I have never found this issue to be a sensor, because the pcm detects a bad sensor and tosses sensor codes.

The pcm kicks on the light after two consecutive drive cycle failures. Meaning the pcm sees the issue two drive cycles in a row. (see other thread as to what constitutes a drive cycle, I've seen it here) It will turn the light off if the code is cleared or if the problem does not exist for three consecutive drive cycles.

Vacuum leaks do appear to the be most common cause.
TB gasket
Rubber vacuum hose connectors
EGR tube cracked

Electrical can be an issue as well.
Corroded battery cables or poor connections
Plug wires touching O2 sensor causing bad reporting.

Interesting is that the diagnostic aids in the FSM say this is commonly caused by a bad MAF and I've yet to come across one that caused it. Seems that because many of us work on our cars and things get bumped etc those are the more common causes.
 


Good info Bill. There just so many spots that a vacuum leak can occur. Esp as the platform gets older things like gasket, hoses and lines get brittle and start to fall apart.

Easiest way to Determine if your car has this code and you suspect a vac leak is to run a idle air count with the engine warm and idling for 5-10 min. Under 45 its a leak.
 
check engine came back and for sure its the same code. will check again after work tomorrow. id like to try that idle air test but cant get my hands on a scanner that can do that. I work at Nissan and only have Nissam special tools. sucks
 
A little trying and a 13mm will have that EGR tube off. Please pull it and check it.

Trust me on this one..lol
(Fought this one for 3 months when it was my corroded battery cables, since then...successfully won the battle about 10 times when it was driving others nuts)
 
RyanL said:
check engine came back and for sure its the same code. will check again after work tomorrow. id like to try that idle air test but cant get my hands on a scanner that can do that. I work at Nissan and only have Nissam special tools. sucks
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Check out Geddys forsale post he had a LS1m Scanner(I have one and there the Shiznits). it will scan codes, parameters, and do 0-60 tests and HP estimates.
 
that scanner sounds pretty cool!^^

so sure enough the code was P-0171 again! startin to get pissed off. check the fix i made on that leaking vacuum line and still good. took a can on brake cleaner and sprayed every single vacuum line and nothing. pulled the plug on the maf sensor and almost stalled. someone mentioned that if you pull the plug on the maf sensor the idle should remain constant. is that 100% true? because i changed my maf sensor about 2 months ago cuz it was coding. the first new one they gave me was faulty second one better but it is a jobber part so possible that it has failed already! i better have a warranty on this lol
 


YOu are subjecting it to go from a reading to running off a table and pulling the plug...ain't exactly a smooth transisiton. I typically unplug them with the car off and most of the time you need to use throttle to start up and let it learn a min or two.

Pull the tube Ryan... pull the tube. You'll blow through a ton of carb cleaner etc looking for leaks, or you can go to the very common one that can't be found with it. The sureness I am conveying is because this is something I find all the time on these engines.
 
oh ok lol i guess i miss understood on that one then. ok so will give the egr a check. ok will give the egr a check monday after work. and if the hoses are fine then what else should i check for cuz im runnin out of things to check.
 
Ok so just finished checking the EGR hoses bill and brand new I even took a couple pictures if you guys would like. But... EGR gasket is looking like it needs to be changed so that could be causing it maybe? If not what the heck do I do next? Starting to get annoyed.
 
I couldn't remove it I got it part of the way out but not fully my hands are a little big for that place. But I held the light to it and even used my small pivot mirror to look all around and it looks like it's brand new. Also found my spark plug wire was almost touching the o2 sensor wire moved it and light went away when I left the garage almost immediately. But was always going on n off.
 


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