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The P0171 Bank 1 lean code is one of the most frequent issues our trucks see as they get older with the 3.4L V6. These can be caused by quite a few things as outlined in the shop manual, but most often it is our MAF. When cleaning the MAF dosnt fix the issue then a replacement will be in order. As with all electronic components the OEM parts are recommended for compatibility and quality. A 96-98 junk yard MAF will run you $50-$100 and may very well suffer the same issues. A new 96-98 MAF from Toyota will be $750 or more. That's why people before me figured out how to use the 99-02 sensors instead.

Parts needed:

-99-02 complete airbox $40-$100 at the junk yard
* a note on these airboxes is they do sometimes break where the MAf tube grafts to the box. There are cheap aftermarket ones available , but I dont know whats best to get so I went OEM

-Denso 197-6020 Mass Air Flow Sensor $75 shipped from amazon
* this is the OEM sensor bought straight from denso

You can see the differences in the airbox at the MAF. The two airbox/Maf combinations are interchangeable Everything mounts and lines up as it should. The only difference is the pin outs on the MAF.


This is the original pin out from my 96. I do not know if the wire colors are consistent across vehicles and years, but the wire positions will still be relevant.


Start by taking out the white keeper with something small and pointy. It slides right out if you pry at it from a couple different spots.


Next is a little tricky to explain but put some gentle tension on the wire while moving the black locking tab downward with a small pointed tool. This retention method is very common if you have ever de-pinned any other style connectors. The arrow here is pointing to a black tab that has been moved down and the wire is ready to come out on the backside.


slide the pins back in for this new configuration and re-install the white keeper.


Results:
For my truck the new MAF gives it better response and power, but this is in comparison to a MAF that is old and faulty. The Long term fuel trims are +15 at idle, and that's higher than normal. My old MAF is +5 for comparison. Anything plus or minus 10 is considered working correctly. The +15 would indicate a vacuum leak in any other situation, but I think its just because the new MAF is significantly less restrictive. Normal driving shows long term trims of zero to +7 with the lowest numbers coming at the highest loads so the MAF is very comparable.
 

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haha things are good! Hope all is well with you too! I'm whittling away at the small issues on the truck now. Pretty sure the rattle I have had for years is my cats guts floating free :/

UY still has viruses after all these years so I posted it here.
 

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Great write up, ive been wanting to do this mod for a while. I finely got all the parts rounded up and swapped all the parts. But I haven't been able to get the 99 Maf mod to work. My truck is a '96 4Runner with a TRD supercharger and a 5speed. The truck will start with the '99 Maf, but stumbles and dies immediately. I'm using a brand new Toyota #22204-21010 Maf, it's not throwing any codes and I can see Maf and iat movement on live stream. Any help would be greatly appreciated! Thanks
 

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Nice informative thread. I've picked up a 99-04 air box that I need to put into my 97 so I need to swap in the 99 style MAF and rewire. Your description and pictures will be very helpful.
 

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I know this is over a year since the original post ... the images are not loading is it possible to upload again or have them emailed? I am possibly looking at having to this modification in the near future and not clear on which wires need to be re-pinned.

Thanks!
 

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I know this is over a year since the original post ... the images are not loading is it possible to upload again or have them emailed? I am possibly looking at having to this modification in the near future and not clear on which wires need to be re-pinned.

Thanks!
Haha I saved the original pictures to my computer just for the event that they disappeared from this thread.

maf_96-98.jpg

maf_96-98_repin.jpg

maf_96-98_repin2.jpg

maf_99-04.jpg
 

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MAF upgrade option

I researched this just a little and found a MAF that would replace the old style. You still have to repin but the 96-98 airbox can still be retained. The donor MAF assy. comes from a Volvo S60 and it is essentially bolt on and very stock looking,Genuine OEM Volvo S60 V70 01-04 Mass Air Flow Sensor Meter #9202199.$20 bucks or so on ebay. I think this is the best option for the budget minded it fit perfectly in mine and I know you won't regret the change.
 
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