Help!!! P0171!!!

fightman80

fightman80

New member
Hey folks,

Well some of you might know, but I have had a Check engine light on my rig now for a little over a week, and after getting it scanned today at Part Source, they told me it was the dreaded P0171 code...or as we all know....O2 Sensor!

Now, that being said, I'm not sure where this sensor is on my truck, and was wondering if any of you could advise, and maybe even provide a link to a thread with the step by steps?? The sensor is $212.00 for an aftermarket piece from Part Source....so I'm looking to save some dough and do it myself!

Any help you guys can provide, would be great!
 
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I did one a few months ago and am about to do the other, CEL light came on with P0136.

Unless you're a California emissions vehicle, there's one sensor before the Cat and another after the Cat.

There's a way to diagnose which one it is with a multi-meter, my bud had an OBD scanner that told me mine.

Check Amazon with correct part number ( Oxygen / AFR Sensors - Underdog Racing Development ), I payed $60 for mine.

Install is super easy and quick, two nuts, plug and play.
 
P0171 is the dreaded 'System too Lean'. Maybe you meant P0141?? (Heated Oxygen Sensor Circuit Malfunction Bank 1 Sensor 2).

If it's P0171, clean your MAF and throttle body, and check for leaks in the air induction system and vacuum leaks in general. If it's the O2 sensor, it will be the front one but it's not the most likely cause, absent any other codes. Dirty or defective MAF is first suspect.

If it's P0141, it's the rear sensor or its wiring.
 
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TheDurk said:
P0171 is the dreaded 'System too Lean'. Maybe you meant P0141?? (Heated Oxygen Sensor Circuit Malfunction Bank 1 Sensor 2).

If it's P0171, clean your MAF and throttle body, and check for leaks in the air induction system and vacuum leaks in general. If it's the O2 sensor, it will be the front one but it's not the most likely cause, absent any other codes.

If it's P0141, it's the rear sensor or its wiring.
Click to expand...

It's definately P0171. The guy at the part store said it read "left bank lean". The guy at the store said it was the Pre-Cat 02 sensor, but I thought I'd search here to confirm. A few of the threads on the forum say it's the 02 sensor and cleaning the MAF did nothing to clear the code. The truck is a little hard to start in the morning, and is hard on fuel.....which were other symptoms someone had posted on the thread.....

What do you think Durk?
 
Do you have any idea how old your front O2 sensor is? If no idea, or its 80K plus, then it's a good move anyway to change it. I'd still clean the MAF and TB and check for air leaks, these cost nothing and I always try the cheap fixes first. MAF issues cause some Po171 issues, but there are many other possibilities, including fuel issues. I didn't see the post, but the O2 is not in the loop for starting, it doesn't even do anything until the motor warms up and goes into closed loop. The MAF, however, is the primary sensor input (along with the temp sensor in the same unit) to the ECU in open-loop (startup). So I stick to my opinion.

If the machine has been neglected...it might be both.
 
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Sounds good man! I'm assuming that the 02 Sensor is original to the truck...as I have never changed it, and the last owner wasn't exactly known for taking care of this rig! The truck now has 181700km's on the ODO...so it's probably due to be done!

As for the MAF.....what do you use to clean it?
 
05110.jpg

'Nuff said. This is the only thing I would use... cuz it's made for it. If you can't find this, some have used some electrical contact cleaner.
1-Pull the MAF out
2-Spray the contacts down inside it as well as the thermistor sensor on the side
3-Let dry
4-Re-install

Mine was throwing this code even when cleaned. I had enough so I replaced the MAF and it has been fine since... sometimes it just needs to be replaced, but try this first.
 
New to you K&N...

Fightman,

I was just looking through your build thread and noticed you just recently got a K&N filter from someone... If you have already installed it, this may be your culprit.:shrug: just thinking out loud...
If I were you, I would clean it this time and see how long it takes for the light to come back on then check the MAF to see if it is gummed up again. If it is, I would go back to a paper filter. Again, just thinking out loud.

Good luck and happy motoring :driving:
 
Nates_NW4Runner said:
Fightman,

I was just looking through your build thread and noticed you just recently got a K&N filter from someone... If you have already installed it, this may be your culprit.:shrug: just thinking out loud...
If I were you, I would clean it this time and see how long it takes for the light to come back on then check the MAF to see if it is gummed up again. If it is, I would go back to a paper filter. Again, just thinking out loud.

Good luck and happy motoring :driving:
Click to expand...

Totally agree. K&N filters and MAF problems are highly correlated. Also agree on CRC MAF cleaner. Lots of how-to's, should be one in the Documentation sticky.
 
I'd start with cleaning the MAF and clearing the code...it's the cheapest route and is a 50/50 shot to fix it...even if the code comes back, you now have a fresh and clean MAF, right?
Try that first, clear the codes, drive her for a week or so and report back :D
 
fightman80 said:
Hey folks,

Well some of you might know, but I have had a Check engine light on my rig now for a little over a week, and after getting it scanned today at Part Source, they told me it was the dreaded P0171 code...or as we all know....O2 Sensor!

Now, that being said, I'm not sure where this sensor is on my truck, and was wondering if any of you could advise, and maybe even provide a link to a thread with the step by steps?? The sensor is $212.00 for an aftermarket piece from Part Source....so I'm looking to save some dough and do it myself!

Any help you guys can provide, would be great!
Click to expand...

P0171, at least in my experience with these motors are often the MAF.

Secondly, go to sparkplugs.com and get your Denso O2 sensors for a lot less than that. It's going to be the pre cat O2 sensor if its indeed the sensor.
 
I'm going to start with the MAF, and go from there. As for the K&N filter, I hadn't installed it yet. I've recently posted a thread regarding K&N filters and any issues they may cause, and NOBODY chimed in to say that they could cause issues with my MAF......:confused:

I've bought the recharge kit, cleaned and oiled it, but have yet to install it in the rig.

Thanks for all the advice regarding the Code, and MAF Cleaning. I'm going to try that stuff first, before going in and replacing my 02 Sensor.
 
I ran a K&N for years without throwing the MAF. Just dont over-oil it. I would dab it with a paper towel before installing after cleaning it, and straight out of the box do it too.
 
Well, I took apart the intake on the truck today, and cleaned what I believe was the MAF sensor.......light came back on!

Just to clarify, the MAF is the unit just past my air box, that has the plug on it?? The top of the unit has Denzo written on it.....did I clean the right device? HA HA HA!

When I disconnected it from the plug and removed it from the intake tubing, I sprayed inside, and the connectors where the plug joins.....did I miss anything??
 
fightman80 said:
Well, I took apart the intake on the truck today, and cleaned what I believe was the MAF sensor.......light came back on!

Just to clarify, the MAF is the unit just past my air box, that has the plug on it?? The top of the unit has Denzo written on it.....did I clean the right device? HA HA HA!

When I disconnected it from the plug and removed it from the intake tubing, I sprayed inside, and the connectors where the plug joins.....did I miss anything??
Click to expand...

I pointed you to this write-up in the sticky: Linky

Did you look at it? He has a '96-'98 which should be the same as yours. Key is getting to the two tiny sensor wires and re-spraying until they are clear of any gunk aka foreign substance.
 
TheDurk said:
I pointed you to this write-up in the sticky: Linky

Did you look at it? He has a '96-'98 which should be the same as yours. Key is getting to the two tiny sensor wires and re-spraying until they are clear of any gunk aka foreign substance.
Click to expand...


Sorry man, I somehow missed that link! :redbrick:! Anyway, I did exactly what the link says....I also let it dry for an hour before re-installing it.

My MAF was actually pretty clean! With all the dirt and grease under my hood, i would have thought the MAF would be just as dirty, but it was spotless inside!

Anyway, what do you think about trying to remove the 02 Sensor and just cleaning that??
 
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