Help!!! P0171!!!

[babowc]

So, I know this thread is way old.. but what were your results?
I changed out my MAF and O2 sensor, but I'm still getting a persistent P0171 code. I did a full tune up and changed the fuel pump, CTS, and added an aftermarket intake (believed the factory intake had leaks?), but P0171 keeps coming back!

I have a 1999 3.4.. This P0171 is the death of me! It won't go away..

 

[RafterTroy]

p0171

I have the same code on mine for a few months now. I have replaced the fuel pump, the MAF sensor, both of the O2 sensors, and the exhaust still getting this code any ideas?

 

[4Runnin2000]

I had the p0171. Did a few things. But it ended up being my maf sensor. Ordered a new one and haven't seen the light since. (knock on wood) that was 3 months ago

 

[astronut203]

New MAF Suggestions

So it looks like it comes down to a bad MAF and I'm in need of replacing it. What's the suggestion for a new MAF? I have seen a lot of names thrown out there and there is a wide range of the prices.

 

[TheDurk]

So it looks like it comes down to a bad MAF and I'm in need of replacing it. What's the suggestion for a new MAF? I have seen a lot of names thrown out there and there is a wide range of the prices.

There are also two different styles based on year and you don't give yours.

 

[Dozerman]

Hey Durk,
thx for all of your inputs they are very helpful!
I have an 1999 4runner sr5 which is non Cal. It is a 5 spd manual trans with the V6 engine. I am the original owner and now have 120K since I usually drive it primarily in winter for the 4WD. (I live in Northeast Ohio area.)
My engine light went on 2k ago and was kind of intermittent on/off. My local mechanic put the analyzer on it and it is a PO171 lean code and said there are many causes a you have been discussing. I carefully cleaned the MAF using the CRC brand cleaner and the engine check light went out w/o clearing the code. This remained for a week and then the light came back on. I purchased both O2 Denso sensors. A friend installed the back sensor but could not replace the front one since he could not get access to the connector. He is doing this using a ramp and working strictly below the vehicle. He claims he has to reach above the pipe and the space is very limited.
Have you changed your 99 4runner front O2 sensor? If so, how were you able to access the connector? I mentioned that I read in the blogs that there were some cases where you remove the sensor first and feed it over the pipe which gives easy access to the connector.
Hope you can help me solve this situation as i do not want to go to Dealer yet.

thx

 

[TheDurk]

Hey Durk,
thx for all of your inputs they are very helpful!
I have an 1999 4runner sr5 which is non Cal. It is a 5 spd manual trans with the V6 engine. I am the original owner and now have 120K since I usually drive it primarily in winter for the 4WD. (I live in Northeast Ohio area.)
My engine light went on 2k ago and was kind of intermittent on/off. My local mechanic put the analyzer on it and it is a PO171 lean code and said there are many causes a you have been discussing. I carefully cleaned the MAF using the CRC brand cleaner and the engine check light went out w/o clearing the code. This remained for a week and then the light came back on. I purchased both O2 Denso sensors. A friend installed the back sensor but could not replace the front one since he could not get access to the connector. He is doing this using a ramp and working strictly below the vehicle. He claims he has to reach above the pipe and the space is very limited.
Have you changed your 99 4runner front O2 sensor? If so, how were you able to access the connector? I mentioned that I read in the blogs that there were some cases where you remove the sensor first and feed it over the pipe which gives easy access to the connector.
Hope you can help me solve this situation as i do not want to go to Dealer yet.

thx

My Cali and your non-Cali are very different. The sensor is lower and further back on yours. In my case, I found the connector was already loose from its mount the first time I did the sensor, and I have never put it back, so changing mine has been a breeze both times I have done it. I suspect it was left loose originally by the dealer when they did a warranty repair ages ago.

 

[astronut203]

There are also two different styles based on year and you don't give yours.

My apologies! 2000 - 3.4

 

[Trip_84]

i could be wrong so maybe someone on here knows. i was under the car taking pictures yesterday so i could have for future references. i circled in red what i think is the sensor and the other pic i think is actually it.

Hopefully someone here can double check it before you think it is the sensor because i am not 100%

 

[TheDurk]

i could be wrong so maybe someone on here knows. i was under the car taking pictures yesterday so i could have for future references. i circled in red what i think is the sensor and the other pic i think is actually it.

Hopefully someone here can double check it before you think it is the sensor because i am not 100%

Yes, that is front O2 sensor.

 

[DarkSideGTI]

My truck was showing codes P0171 and P0420 Catalyst Efficiency Below Normal. I figured it was a bad O2 sensor, but the computer at AutoZone was recommending a MAF sensor and after reading this thread I figured I would start with the MAF. So I bought some MAF cleaner and sprayed it out as well as disconnected the battery to clear the codes. How many miles does it usually take for the code to pop back up? I am selling my truck soon and want to make sure I nip this problem in the butt first rather than having it pop up for the buyer.

 

[DarkSideGTI]

My truck was showing codes P0171 and P0420 Catalyst Efficiency Below Normal. I figured it was a bad O2 sensor, but the computer at AutoZone was recommending a MAF sensor and after reading this thread I figured I would start with the MAF. So I bought some MAF cleaner and sprayed it out as well as disconnected the battery to clear the codes. How many miles does it usually take for the code to pop back up? I am selling my truck soon and want to make sure I nip this problem in the butt first rather than having it pop up for the buyer.

Well over 100 miles now since cleaning the MAF and it is CEL free still. I'm hoping that it did the trick.

 

[TheDurk]

Well over 100 miles now since cleaning the MAF and it is CEL free still. I'm hoping that it did the trick.

To be sure, get it scanned again and have them tell you if the catalyst test cycle shows COMPLETE. You are probably good on on P0171 too, but a read will also show if there is a pending P0171. It takes two trips to set a P0171. So if nothing pending, then I'd say you are definitely good there, too.

Or get your own scanner, either a cheap handheld or a Bluetooth you can use with your phone.$20. No excuse for not owning one, in my opinion.

 

[DarkSideGTI]

To be sure, get it scanned again and have them tell you if the catalyst test cycle shows COMPLETE. You are probably good on on P0171 too, but a read will also show if there is a pending P0171. It takes two trips to set a P0171. So if nothing pending, then I'd say you are definitely good there, too.

Or get your own scanner, either a cheap handheld or a Bluetooth you can use with your phone.$20. No excuse for not owning one, in my opinion.

I stopped off at AutoZone on the way home from work last night and had it scanned. There were 0 codes, so I am hoping the problem is fixed now.

 

[TheDurk]

I stopped off at AutoZone on the way home from work last night and had it scanned. There were 0 codes, so I am hoping the problem is fixed now.

Did you ask the question if all the tests were COMPLETE? The lazy AZ guy won't look at it unless you ask him. It's another button to push and it doesn't lead to an easy sale so they have no reason to bother.

 

[tystaco]

2000 3.4 Auto has been acting funny up steep hills, chugging sound, maybe a loss of power. I was thinking I had it narrowed down to a plugged cat or muffler, had it at the shop today for a test and the muffler guy says I have an existing and current P0171 code. Not sure if the check engine light is burned out as it has never been on since we've owned this since November, or if his scanner can see a little more than I am? He thinks that the cat might be burned up due to running lean for so long.

I ordered a Bluetooth scanner today, will be here Friday. I will clean the MAF tonight, as I definitely didn't pull it apart to clean the two silver wires when I did it when I first got it. I don't want to throw parts at it after reading the cost of MAF's and O2 sensors, but I need to know that we can go up hills without doing serious damage to the rig.

I have an ohm meter, and will have the scanner. Anyone know of quick links detailing what and how to test the O2's? I've seen #'s tossed out on here for resistance as well as voltage to watch for with the OBDII scanner plugged in, but any more info I can take in will better prepare me for battle.

 

[19963.4lsr5]

You can't really test a O2 sensors functionality with a meter. Only the heater portion can you test. The sensor side you can look at with in scope or graph mode and see if it's cycling hi and low correctly.

Have you replaced your fuel filter, it's the first step is take if it wasn't done yet.


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[tystaco]

You can't really test a O2 sensors functionality with a meter. Only the heater portion can you test. The sensor side you can look at with in scope or graph mode and see if it's cycling hi and low correctly.

Have you replaced your fuel filter, it's the first step is take if it wasn't done yet.


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Fuel filter, plugs, wires, and coils are all new as of about 5 months ago. Also cleaned the TB and changed PCV, but as I said, when doing the MAF I mistakenly only looked and saw that the brown bulb was clean and put it back together.

 

[19963.4lsr5]

Then clean the MAF sensor or think about replacing the preCat O2 sensor. Or figure out what's needed to check fuel pressure.


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[4Runnin2000]

When I had this code I replaced the front o2 since it was the cheaper than the MAF. Didn't work. So I replaced the MAF and it's been good for a year now. I would just replace the MAF if cleaning it doesn't work. I think I got the denso on rockauto for 60 or 70 bucks.

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