P0171 - System Too Lean Bank 1

[clanofwolves]

You need to repost the results after the engine is fully warmed up. Include rpm and TPS.

Try and switch your readings to American measurements if you can.

Will do and will post.
Thanks!

 

[LittleCaesar]

At least with the preliminary data, not a vacuum leak and probably not a direct fuel problem. Most likely an aging sensor. Post the new data once you have it.

 

[clanofwolves]

You need to repost the results after the engine is fully warmed up. Include rpm and TPS. Try and switch your readings to American measurements if you can.

This better? What's it tell ya?

...again, thanks in advance!

 

[Bad Luck]

I would replace the oxygen sensors

 

[19963.4lsr5]

Here is mine from this afternoon after a drive to the grocery store and back, sorry it’s upside down.

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[LittleCaesar]

+1 on changing out the 02 sensors.

Any drivability issues with the check light engine on?

 

[clanofwolves]

+1 on changing out the 02 sensors.

Any drivability issues with the check light engine on?

I'm going with the upstream O2 and see what it does. It seems to drive an accelerate fine, but she has stalled every once in a while when at a light with the AC on.

 

[LittleCaesar]

I would save your pennies and get both, but definitely replace the upstream if money is tight.

Ever cleaned the TB/IAC?

 

[sroosma]

I had this code right after I half-assed cleaning my MAF sensor. What I did was fully clean it and reset the ECU and it hasn't come back (that was months and a couple thousand kms ago). Not saying that it isn't the O2 sensor, by any means, but you may as well try and clean the MAF to see if that does anything before replacing parts. Probably best to clean TB/IAC while you're in there, too. good luck!

 

[clanofwolves]

I would save your pennies and get both, but definitely replace the upstream if money is tight.

Ever cleaned the TB/IAC?

I will on the O2s... I do some seafoam cleaning of the TB and I spray cleaner into the IAC when I am cleaning the MAF (the right brass screw is removed with a vice grip as the first attempted removal found her not budging, haha). I haven't paid an overwhelming amount of attention to the IAC, save I just insure she moves easily.

 

[19963.4lsr5]

I will on the O2s... I do some seafoam cleaning of the TB and I spray cleaner into the IAC when I am cleaning the MAF (the right brass screw is removed with a vice grip as the first attempted removal found her not budging, haha). I haven't paid an overwhelming amount of attention to the IAC, save I just insure she moves easily.

I pull the lower idle assist hose off the IAC and spray in there until no black chunks are visible in the inlet to it.


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[clanofwolves]

At least with the preliminary data, not a vacuum leak and probably not a direct fuel problem. Most likely an aging sensor. Post the new data once you have it.

I would replace the oxygen sensors

+1 on changing out the 02 sensors.

What is the best brand (other than OEM) that you guys have had good luck with?

 

[bear1998]

Denso....

 

[Bad Luck]

I replaced mine with Denso

 

[19963.4lsr5]

NTKs work also


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[LittleCaesar]

Been using the same Densos since 2009 with zero problems......

 

[Grizzly Be4R]

Hi everybody, I'm new to the forum trying to diagnose a P0171 code on my (new to me) '01 SR5.
So far, I've solved my P1135 & P0420 codes by replacing both O2 sensors with Denso.
For the unsolved P0171, I tried cleaning my MAF but the code returned. My next task was gonna be to check for a vacuum leak. Not sure if there's any common things I'm missing or could try? Thanks in advance for any input.
i recently bought the truck and the dealer didn't disclose multiple check engine codes so I'm hoping this is an easy fix

 

[JoeT4R]

Hi everybody, I'm new to the forum trying to diagnose a P0171 code on my (new to me) '01 SR5.
So far, I've solved my P1135 & P0420 codes by replacing both O2 sensors with Denso.
For the unsolved P0171, I tried cleaning my MAF but the code returned. My next task was gonna be to check for a vacuum leak. Not sure if there's any common things I'm missing or could try? Thanks in advance for any input.
i recently bought the truck and the dealer didn't disclose multiple check engine codes so I'm hoping this is an easy fix

One toyota website suggests vacuum leaks like you're saying, but it also goes on to say that it could be a leak in the PCV hoses or even the valve itself.

If you replace the PCV valve, make sure you get a new grommet to go with it and take your time. Get it from Toyota, they are inexpensive. Have needle nose pliers on hand in case it begins to crumble and you get bits down
in the hole it comes out of.

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[JoeT4R]

Get or find someone with a smoke machine. It'll save you a lot of time and money.

This too!

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[Grizzly Be4R]

Mechanic didn't detect a vacuum leak. Changed the MAF (new Delphi) and also replaced the PCV valve+ gasket.
CEL stayed off for about 100 miles and then popped back on. P0171. O2 sensors are new as well. Any other suggestions? I'll try to get a smoke test done soon if that's my only option besides the fuel filter..