P0171: System too Lean (Fuel Trim) (1 Viewer)

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Start basic, swap the fuel filter. Cut the old one open and see how nasty it is. I got a dirty tank of fuel once in my 100, loaded up a brand new filter pretty good. I didn't do my troubleshooting very well and ended up burning up a fuel pump. New filter and new pump and it was 100% again after having very similar (but more advanced) issues like you described.
 
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Start basic, swap the fuel filter. Cut the old one open and see how nasty it is. I got a dirty tank of fuel once in my 100, loaded up a brand new filter pretty good. I didn't do my troubleshooting very well and ended up burning up a fuel pump. New filter and new pump and it was 100% again after having very similar (but more advanced) issues like you described.

That would be a good call. Couple things - USDM 200s don't have fuel filters. Only the fuel sock. Also, I would expect a flow issue to effect high load fuel trims more but I'm not seeing that.

Watching the fuel trims, it seems like light load is where I'm seeing the most issue. This may be correlated to what @bloc pointed out earlier in that our fuel pumps have a variable voltage fuel controller, and the pump is struggling at lower voltages. With intermediate to higher loads, and associated voltages, the pump seems to do better.

I could debug more and jump the pump directly with 12V, but I'll probably just change it at this point.

Keeping an open mind and this all remains to be proven. I've got a pump in hand, tools to tackle this, and now just need a free weekend.
 
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Similar situation here.

Codes: P0171, P0174, P0607
  • Symptoms: fast-blink 4Lo, TRAC, and CEL. Also, very low MPG (adding fuel due to lean condition above, assumed), and rich-smelling exhaust.
  • First identified: long uphill slog, rocky, lots of very slow driving, nose-up
  • Other details: Christmas Dash started at very end of aforementioned trail, at top of mountain. Truck would not go out of 4Lo or unlock CDL. Let cool over night, neg battery terminal pull in AM with 4Lo switch to 4Hi while disconnected. Disengaged 4Lo upon startup (zip-clack sound from diff actuator, as expected) and X-Mas Tree went away.
  • Still more otherly details (TechStream):
    • Atmosphere Pressure: -2 (negative seems very strange, since not in Death Valley or outer space)
    • MAF: 9.48 gm/sec
    • O2S B1S2: 0.41
    • O2S B2S2: 0.39
    • AFS Current B1S1: -0.48 ma
    • AFS Current B2S1: -0.42 ma
    • O2S Impedance B1S2: 184.8 ohm
    • O2S Impedance B2S2: 181.23 ohm
    • LTFT: B1S1: 27.3
    • LTFT B2S1: 28.9
    • Air pump pressures all negative
    • (not all sensors set)
  • Remediation to-date:
    • first clean MAF, then replace
    • replace PCV valve
    • filter check
    • one tank run with injector cleaner (foam-somthing)
  • Next steps
    • smoke test
I have on my list to drop the 25G LRA, because the breather system was not installed correctly by [redacted] in [redacted], where they apparently did a [redacted] job.

FF data for P0171 below.

1659117848401.png


1659117873378.png


1659117888260.png
 
Last edited:
Joined
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Messages
7,805
Location
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Similar situation here.

Codes: P0171, P0174, P0607
  • Symptoms: fast-blink 4Lo, TRAC, and CEL. Also, very low MPG (adding fuel due to lean condition above, assumed), and rich-smelling exhaust.
  • First identified: long uphill slog, rocky, lots of very slow driving, nose-up
  • Other details: Christmas Dash started at very end of aforementioned trail, at top of mountain. Truck would not go out of 4Lo or unlock CDL. Let cool over night, neg battery terminal pull in AM with 4Lo switch to 4Hi while disconnected. Disengaged 4Lo upon startup (zip-clack sound from diff actuator, as expected) and X-Mas Tree went away.
  • Still more otherly details (TechStream):
    • Atmosphere Pressure: -2 (negative seems very strange, since not in Death Valley or outer space)
    • MAF: 9.48 gm/sec
    • O2S B1S2: 0.41
    • O2S B2S2: 0.39
    • AFS Current B1S1: -0.48 ma
    • AFS Current B2S1: -0.42 ma
    • O2S Impedance B1S2: 184.8 ohm
    • O2S Impedance B2S2: 181.23 ohm
    • LTFT: B1S1: 27.3
    • LTFT B2S1: 28.9
    • Air pump pressures all negative
    • (not all sensors set)
  • Remediation to-date:
    • first clean MAF, then replace
    • replace PCV valve
    • filter check
    • one tank run with injector cleaner (foam-somthing)
  • Next steps
    • smoke test
I have on my list to drop the 25G LRA, because the breather system was not installed correctly by [redacted] in [redacted], where they apparently did a [redacted] job.

FF data for P0171 below.

View attachment 3072400

View attachment 3072401

View attachment 3072402

Sorry you're dealing with that and hopefully we both can get back on the road soon. Curious how many miles you have on your 2008?

I haven't looked too closely into most of the other numbers but these two jump out. With trims that high, I would think drivability is showing issues?
  • LTFT: B1S1: 27.3
  • LTFT B2S1: 28.9
Smoke test is not a bad idea. Good think is that almost all the vacuum system is easily reachable on top of the motor. It may be useful to use plugs to isolate things like the PCV, fuel system, intake, to see if it changes anything.

Here's a cheap fuel pressure tester that plugs in super easy to test. That would show the smoking gun if it's the fuel pump side of things
Amazon product
 
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I'm almost thinking with the huge fuel pump recall, whether there's been systemic issue outside of the recall range. That Toyota simply identified a cut-off that served their scope and risk? Fortunately 2013+ will all have their fuel pumps replaced, so leaving a smaller range or 200-series needing to add another item to their watch list in higher miles.

While 140k miles is a lot, in the grand scheme of things, a fuel pump at this mileage is somewhat premature. For a Land Cruiser of all things. Much like the radiator crack or transfer case solenoids.
 

Moby

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I put 240k on my 3FE fuel pump, so would agree it seems premature.

What is the fuel pump recall? My dealer has never mentioned this for my 2020
 
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I put 240k on my 3FE fuel pump, so would agree it seems premature.

What is the fuel pump recall? My dealer has never mentioned this for my 2020

I don't know the complete list of ranges for the 200-series, but it's extensive in Toyota and Lexus vehicles.

From what I know, it effects Toyota/Lexus model years as early as 2013 to 2020.

Similar but is not limited to this set
1659126754911.png
 
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Just creeping up on 160k. No discernable drivability issues.
 
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It’s a thing of beauty

View attachment 3068909

Working through it now and referencing your pics in your aux tank other thread. Thanks for the useful insights.

Just got all the hoses undone and disconnected. Was ready for a fight but the vent tube wasn't bad as I think I tackled it before with the LRA tank install. Couple strategies I used for others
- brown guard slides up, and hides a standard fuel fitting with buttons on either side
- it's possible to twist the hose 180* to expose the buttons better from the other side of the brown guard
- hose pliers to help squeeze the buttons and gently work the fitting off

1659726422750.png
 
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The b*tch is out. Actually wasn't too bad and the USDM cruisers have less connections being a single tank. A skilled tech could have this out in probably 30 minutes from underneath. There was some discussion about going in from the top and modifying the access cover hole to extract the pump that way. Surely underneath is easier, albeit dirtier.

1659732765156.png
 

bloc

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The b*tch is out. Actually wasn't too bad and the USDM cruisers have less connections being a single tank. A skilled tech could have this out in probably 30 minutes from underneath. There was some discussion about going in from the top and modifying the access cover hole to extract the pump that way. Surely underneath is easier, albeit dirtier.

View attachment 3078457
Based on that picture I’ll remove the access hatch and hose off the top of the tank as best I can before removal.. if I ever need to do this job.

Just a thought.. did you get the gasket for the pump module lock ring?
 
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The b*tch is out. Actually wasn't too bad and the USDM cruisers have less connections being a single tank. A skilled tech could have this out in probably 30 minutes from underneath. There was some discussion about going in from the top and modifying the access cover hole to extract the pump that way. Surely underneath is easier, albeit dirtier.
You, sir, are an amazing Cruiserhead. Thorough. Well sorted. Well documented. Nice work!
 
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Based on that picture I’ll remove the access hatch and hose off the top of the tank as best I can before removal.. if I ever need to do this job.

Just a thought.. did you get the gasket for the pump module lock ring?

It's all sealed with minimal risk contaminating things while lowering the tank. Shop vac with a brush head worked wonders and to your point, is important to clean before opening up seals.

Yup to gasket and threw in a new one. My original was clean as a whistle and I wouldn't hesitate re-using. What I would maybe change for incrementally more cost if I had to do it again is the fuel gauge sender while in there. They've been known to go bad once in a blue moon.

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1659740951432.png
 

MoJ

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Interested to see the resulting data and whether it solves the issue which might be tough to reproduce given the conditions
 

bloc

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Good call on the sender.. a relative with a different toyota vehicle but similar generation has had issue with it.
 
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Bingo. New fuel pump did the trick returning idle fuel pressure to 41psi and practically zeroing out LT trims - .8 and 1.6. Wasn't too bad of a job. I'll write it up later.

1659754854310.png
 
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Bingo. New fuel pump did the trick returning idle fuel pressure to 41psi and practically zeroing out LT trims - .8 and 1.6. Wasn't too bad of a job. I'll write it up later.

View attachment 3078853
Exceptional work as always. Really may give merit to your theory about limiting recall scope. Now dissect the old one to see how it began to fail……
 

bloc

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Exceptional work as always. Really may give merit to your theory about limiting recall scope. Now dissect the old one to see how it began to fail……

Didn't think I could tear apart the pump effectively, but you encouraged me to give it a short. Was easier than expected.

Cut apart filter sock - looks good.
1659888206659.png


Working the head off like a tin can. Can already see that the pump impeller fins have wear.
1659886837808.png


There's clear wear inside on all surfaces with impeller runout. You can see on the circumference of the housing left of the arrow wear from the impeller. On the impeller itself, aluminum transfer marks on ~1/3 of the wheel showing contact with the housing.

1659888402782.png


Housing and cap showing wear.
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The impeller to motor shaft wasn't even clearance fit and slips right off. I attribute the original failure to wear at this interface, allowing play and slop of the impeller.

In the larger Denso fuel pump recalls, they note - Low-density impellers inside Denso branded fuel pumps are cracking and limiting the amount of gas reaching the engine. In that failure mode, it would be catastrophic. Albeit more a brittle failure mode. Fundamentally, it still indicates that the impellers may be low-density and weak.

I believe in my case, that weakness manifested in wear at the shaft to impeller interface driving more premature wear. A slow degradation like failure mode wouldn't necessarily be subject to a recall, but 140k miles for a Toyota / Denso design, on a Lexus / Land Cruiser doesn't meet expectations.
 

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