CEL and p0171 code

[Ric]

just wanting your alls thoughts, and ideas.
Heres my issue:
the CEL came on got the code checked p0171.
So Ive cleaned everything, to include the filter (TrueFlo) the MAF (i think thats the sensor in the airbox tube) reset the EFI fuse, was good for about a week, the CEL came back on, recleaned again, but Im "thinking" the O2 sensor is either going bad or is bad.
heres vehicle details:
99 4runner, 185K miles, replaced the O2s at about 100K, reg.
How many miles does the O2 sensors last ?

I was thinking about replacing the front O2, unless you all have any suggestions.
thankx for any advise.

[Good Times]

with 185k miles have you ever replaced the maf sensor? though i'm thinking those last forever oddly my gf's 00 corolla with only 65k miles didn't (weird but repacing the maf sensor did the job after 4 cleanings..)

not sure about the o2 as i thought those threw diff codes... dunno.. hopefully mtl_4runner (jamie) will chime in on this as he's definitely posted a lot about po171 codes.

[Ric]

Good Times,
thankx for the reply, no the MAF hasnt been replaced, i did look for something on the p0171 didnt see anything, ill look some more..

[DoubleZero4x4]

When I had to replace my O2 sensor, I had multiple codes P0171, P0133 and P0131. When I had to replace my MAF it was a P0171 by itself.

Is your gas mileage suffering with the CEL? I ask this because this was also a symptom when it was the O2 sensor.

[YotaFun]

DoubleZero Is right on top of it.

When my o2 Sensor was going I had really pour gas mileage and the end ran a little more rough.

But I had a P0136 code for the rear.
So it might def be time for a new MAF.

[MTL_4runner]

Ric, first thing to do is to try and clean the MAF with some brake cleaner.

Here's a good thread on that:
http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=1033.0

If you clean it thoroughly (don't worry about being very liberal with the cleaner....just be sure to let it fully dry before starting the motor again), you pull the negative batt terminal, drive it and the P0171 code still comes back, then start looking for a replacement MAF sensor (there are cases where the MAF sensor is "bad" and no amount of cleaning will make it work again). It is possible that something else is causing that particular code, but 9 times out of 10, the MAF sensor will be the culprit.

[Ric]

MTL_4runner,
I was wondering if the MAF ever goes bad, I have replaced the front O2 sensor, (last week)trany flush, brake flush, coolant flush (i know them have nothing to do with the 171 code) but it was time.

well after replacing the front O2 it was fine for a week, then today, going on a run (pics will be up later) it came back on, my buddy (Jamie) brought his code reader, and yes, it was 171. again.. :headscratch:
pulled the EFI, topped off with gas, put it in, was fine all day.
Then on the way home, right about the same place, it came back on, I keep my stuff clean, air filter, MAF etc. but Im thinking about just replacing the MAF, it does have 200K miles on it, and is driven hard, :D
Im starting to think my baby is getting tired of wheeling :rofl:

Thankx for all the help and advice.

[MTL_4runner]

If you already tried cleaning with brake cleaner and you're still getting the P0171 code then yep, it's time for a new MAF. :D

[firebane]

I just wanna add a comment in here saying that I took a look at my MAF sensor and its not the same as this picture:
http://www.4x4wire.com/toyota/maintenance/tacoma_4runner_30k/wires_clean.jpg

They have changed it in my 99 3.4 or maybe I have the wrong one and looks like this:
http://www.globaldensoproducts.com/images/airflow_meter.jpg

And I'm probably gonna roughly say that they have designed this in a way that made it work better and more efficiently but if it craps out then it'll need to be replaced as there is nothing more than a small bulb on the end that hardly gets dirty.

[Ric]

firebane,
mine is like the one in the second pic

[MTL_4runner]

Uh, guys......those are the same part are they not?
One you're looking at it straight on and the other is a side view.

[firebane]

One in the picture has two small wires and the one in the 2nd picture is two thick wires with a bulb on the end.

I'm checking parts #s if I can find them

[MTL_4runner]

One in the picture has two small wires and the one in the 2nd picture is two thick wires with a bulb on the end.

I'm checking parts #s if I can find them


MAF for a 99-02 V6 4runner is part number 22204-07010.

The same MAF P/N was also on:

4Runner 99-02 (6 cyl, 5VZ-FE eng)
Avalon 00-04
Camry 02-06 (4 cyl)
Highlander 01-05 (6 cyl)
Lexus ES300 99-01
Lexus RX300 99-03
Prius 01-03
Scion TC 05-06
Sienna 01-03 (6 cyl, 1MZ-FE eng)
Solara 02-06 (4 cyl)
Tacoma 99-04 (6 cyl)
Tundra 00-04 (6 cyl, 5VZ-FE eng)


22204-21010 is an old part number.

[Ric]

ok heres an update on mine:
as far as cleaning it, (call me a moron) but Ive never pulled the MAF off the air tube, just cleaned the one part that has two metel peices conected together.
Since Ive never actually pulled the MAF off, the tube, to see the two resistors, they have never been cleaned, until today, :D wooow was it dirty in there, but thankx to you all :thumbup: its clean, and running like a race car, ok, maybe not, lol.
again, thankx for all the help, :clap:

[MTL_4runner]

Hopefully no more CEL for a while Ric. :thumbup:

[firebane]

One in the picture has two small wires and the one in the 2nd picture is two thick wires with a bulb on the end.

I'm checking parts #s if I can find them


MAF for a 99-02 V6 4runner is part number 22204-07010.

The same MAF P/N was also on:

4Runner 99-02 (6 cyl, 5VZ-FE eng)
Avalon 00-04
Camry 02-06 (4 cyl)
Highlander 01-05 (6 cyl)
Lexus ES300 99-01
Lexus RX300 99-03
Prius 01-03
Scion TC 05-06
Sienna 01-03 (6 cyl, 1MZ-FE eng)
Solara 02-06 (4 cyl)
Tacoma 99-04 (6 cyl)
Tundra 00-04 (6 cyl, 5VZ-FE eng)


22204-21010 is an old part number.


Good info.. may I ask where you found it?

[Ric]

:chair: ok i lied, sorta, i just went to the store, and the damn the came on again :chair: looks like Ill be calling around for a new MAF.. it does have 200K miles on it, :D
it needs to be replaced anyways.

We was talking today, Ive "never" owned a vehicle with 200K on the clock, not even close, i think the most was somewhere around 100K and YES,,, that also was a Toyota, :D my little 82 pick up, oh well, Ill give her some lovin, shes been very good to me, up till now :D

[MTL_4runner]

Good info.. may I ask where you found it?


The national used autoparts interchange database.
Most junkyards will have access to this if you ask.

[02-4Run]

Ric/MTL,
You mention using Brake cleaner, but at Advanced Auto Parts store this weekend I see they sell MAF cleaner. I'm assuming the same thing as brake cleaner? I'm assuming MAF cleaner is the better option to use if its on the shelf, right?

[Ric]

Ric/MTL,
You mention using Brake cleaner, but at Advanced Auto Parts store this weekend I see they sell MAF cleaner. I'm assuming the same thing as brake cleaner? I'm assuming MAF cleaner is the better option to use if its on the shelf, right?

yeppers,

[MTL_4runner]

Ric/MTL,
You mention using Brake cleaner, but at Advanced Auto Parts store this weekend I see they sell MAF cleaner. I'm assuming the same thing as brake cleaner? I'm assuming MAF cleaner is the better option to use if its on the shelf, right?


I haven't looked at what chemicals the MAF cleaner contains, but I can tell you both are fine to use and alot of techs at Toyota don't bother with MAF cleaner at all. In fact, they often just grab the brake cleaner instead. I use the brake cleaner myself because it's cheap, plentiful, you can never have enough around for degreasing and does an excellent job cleaning the MAF. Use whatever you want except the electrical contact cleaner....it doesn't clean nearly as well as the other two.

[firebane]

Not to jack this thread but I'd be posting yet another under this exact thread. Now I'm getting this code and this CEL and its showing on my scanner that Fuel Sys 1 is CL (Closed Loop) and the Fuel Sys 2 is not, and I was gonna just start replacing the o2 sensors but I called the dealership and they are $230 and $250 and was wondering do I HAVE to replace with toyota parts?

MAF sesor seems fine, so I was thinking of replacing the front o2 sensor as the truck has 140,000km on it and I don't know when it was replaced.

[MTL_4runner]

Not to jack this thread but I'd be posting yet another under this exact thread. Now I'm getting this code and this CEL and its showing on my scanner that Fuel Sys 1 is CL (Closed Loop) and the Fuel Sys 2 is not.

MAF sensor seems fine, so I was thinking of replacing the front o2 sensor as the truck has 140,000km on it and I don't know when it was replaced.


Ok, first what scanner are you using? I'm not familiar with Fuel Sys 1 and Fuel Sys 2 unless your scanner is referring to bank 1 and bank 2. If that is the case it makes sense since you don't have any bank 2 sensors on that vehicle (therefore it could not possibly be running in closed loop).

What makes you say that the MAF is fine? There are other things it could be as I mentioned but unless you have recently replaced the MAF, that is usually the first place to start when you get the P0171 code.

Here's what the FSM has to say on the subject:

P0171 System too Lean (Bank 1)

Detected Condition
When air fuel ratio feedback is stable after engine warm up, fuel trim is considerably in error on the RICH side (2 trip detection logic)

Trouble Area

Air Induction System Leak
Injector Blockage
Mass Air Flow Meter
Engine Coolant Temperature Sensor
Fuel Pressure
Gas Leakage from the Exhaust System
Open or Short in the Oxygen Sensor or associated wiring
Oxygen Sensor Defective
Engine Control Unit





I was gonna just start replacing the o2 sensors, but I called the dealership and they are $230 and $250 and was wondering do I HAVE to replace with Toyota parts?

If you want to replace the O2 (A/F) sensors, then give URD a call because they have the best prices going right now. You should only be replacing the front one because one behind the cat doesn't affect the closed loop on the fuel injection and is only used to check converter condition and operation. So wait until it throws a rear sensor specific code (such as P0141) before changing that one.

http://www.urdusa.com/product_info.php?cPath=9_13&products_id=430006000