P0171 P0174: Those pesky lean codes!!!

I have been long time lurker here in Tundras but just joined today as a member. I have been having some ongoing and frustrating issues with my '11 4.6L 4x4 Tundra I was hoping to get some help. I am getting intermittent lean codes (P0171, P0174) on bank 1 and 2 and also a start-ability code (P1604). I appreciate any help you guys may provide.

Let me also provide some "history" that may be relevant. Again, the truck is a 2011 4x4 4.6L. I bought the truck back in 2013 with 75,xxx miles from a used car dealer on the "shady" side of town, not relevant. The truck currently has 168,xxx mile. Initially, the truck ran flawless except for one minor issue; for some reason the truck was very difficult to fill with fuel, it would keep "popping" the fuel full/stop lever on the fuel pump nozzle when I tried to fill up with gas. This was quite an annoying problem as there were times when it would take 10-15 minutes or so just to fill the tank with fuel. I had the local Toyota dealer diagnose that problem and they recommended a new charcoal canister at a cost of roughly $1200 installed, which I declined. After checking the interwebs, I found the likely culprit to be a clogged fuel tank vent hose so I pulled the charcoal canister and vent hoses, blew them out with compressed air and that beautifully solved the gas tank pumping issue.

Back to the main story...Long about 100,xxx miles, the truck would occasionally (every 2-3 months?) throw a CEL light that would also illuminate the Traction Control light a 4LO light. I (naively) assumed it was probably just an O2 sensor starting to fail so when the CEL light would come on, I would just reset it and keep on driving and diagnose it "one day when I had time". Then, about 120,xxx miles I started to notice the engine would, very occasionally and intemintently, "cut out" (some locales may call it a "miss") at higher speeds (60-70mph) or, more often, cut out when I pulled a load with my utility trailer. When I first noticed the miss/cutting out issue at 120,xxx miles, I replaced the spark plugs with DENSO OEM plugs, which did not resolve the issue. From the time I initially noticed the "cutting out" up to now, the "cutting out" issue has increasingly become worse as well as the frequency of the CEL/TC/4LO light illuminations and the truck has also developed a 3rd problem, it is becoming increasingly harder to start when warm (normal operating temps). The truck fires right up when cold but when warm, it will sometimes take up to 5 or so extra seconds to start. When it does finally start, it is not a "strong" startup, it is more like a coughing, sputtering startup for the first few seconds.

Fast forward to now, the truck currently has 168,xxx miles and it has me worrying that soon it might leave me stranded. Within the last month I have had the truck to our local small town Toyota dealership mechanic twice, and he has used the Toyota Techstream laptop and he could not specifically pinpoint any specific issue. He did recommended possibly replacing downstream catalytic convertors (really?) for the "cutting out" issue but could not make a recommendation on the starting issue since he was not able to replicate the difficult starting issue while the truck was at the dealership. Also, in Hail-Mary style frustration, I have replaced the following parts myself, none of which have resolved any of the issues mentioned. In the last month I have replaced spark plugs (for the 2nd time) using Denso Iridium plugs (applied anti-seize on threads), installed new Denso coil packs, (used dielectric grease on plug tip and coil boots), replaced right and left side upstream and downstream Denso O2 sensors, installed new Denso MAF mass airflow sensor, have spent nearly an hour visually checking for a vacuum line leak (found none), and cleaned the throttle body as good as I possibly could with some carb cleaner. I am currently at a loss for what to check but my thoughts are perhaps a sticky PCV valve, clogged fuel filter or possibly a fuel pump slowly failing. From my understanding, there is no externally mounted fuel pump or fuel filter on the Gen2 Tundra but rather the fuel filter and fuel pump are both located inside the fuel tank and the filter is a sock style filter and not a metal tube style filter. Oh, and all replacement parts that I installed are OEM DENSO parts, not aftermarket parts.

FYI, The lead dealership mechanic has been the mechanic to look at the truck both times and he seems very honest and knowledgeable. He also has Master Certification with Toyota and 30 years on-the-job experience. He also mentioned that the Tundra fuel pumps have been very reliable and they have yet to service a Tundra for a failed fuel pump.

 

I had to track these down on my BMW. They're not fun. It turned out to actually be a couple of things. I ended out replacing all of my 02 sensors (upstream and downstream), the MAF, all of the o-rings attached to anything related to the intake, a couple of the PCV system pieces, as well as all of the vacuum line tubing. Ultimately I finally did seal it up and the codes went away, but it was a chore.

You're not going to find all the minor vacuum line leaks via visual inspection. It's just not possible. There are too many places where air can get in and even a small leak can throw a code. There are YouTube videos about how to find leaks by spraying carb cleaner onto places where a leak could potentially show up, as well as using a smoke machine to find them. You'll also want to get an OBDII reader to do some long and short term fuel trim testing to see if you actually have a vacuum leak. Again, YouTube is your friend here.

If you do have a vacuum leak, you have your work cut out for you. I would start at the air box and work your way back to the intake manifold. Look at every piece for cracks. Pull them off and give them a good inspection. Sometimes a crack won't show up w/o flexing the part a bit. If you're not seeing anything then you'll want to physically touch all of your vacuum lines to make sure they're still good. At that age I would think they're still okay, but who knows. Once that is done, it's time for the o-rings, gaskets, intake plugs and anything the engine uses to recycle gases (like the PCV). You'll have to do some research and use some common sense to find them all, but it's worth doing. I found that the tiny ones on my air distributor piece on top of the intake manifold were worn on the BMW. Nobody even mentioned that on any of the YouTube videos I found, but I found them by being methodical and thorough about going over everything as I was removing it. Gaskets are generally cheap, so even if it looks and feels okay you might as well replace it while you have the part off.

If you don't have a vacuum leak, then it's possible that the sensors aren't playing nice with the computer. I had that happen as well. The computer did not like the aftermarket sensors I had bought. Once I put in OE ones things worked like they were supposed to. I'm assuming that's probably the same for Toyota's.

Good luck!

 

Thanks, Sas! That was quite an informative post. I can only guess your frustrations as you physically inspected each vacuum line. I am definatrly not looking forward to that! It has got to the point of frustration though that I have seriously considered starting to look at newer trucks. At what point with your BMW point did you determine it was vacuum lines and not the fuel pump? Did you take several psi readings at the fuel rail over time?

 

Yeah, you just have to get in the mindset that it's going to suck and that you need to be methodical about it. Once that's sunk in, it's a doable job.

Getting enough fuel was one of the tests I did (YouTube again lol), but I didn't take actual PSI measurements. I had also replaced the fuel filter as part of its normal maintenance since I didn't know when it had been replaced last. If you haven't done yours yet that might be a good place to start. I removed and cleaned the fuel injectors and also replaced all the o-rings on them too while I was in there. I think I replaced an o-ring or two on the fuel rail as well, can't quite remember now.

 

I agree that gaskets are cheap and good preventative maintenance “best practices” would be to replace all gaskets while the part is disassembled. However, the truck is only 7 years old. I am pushing 50 years and drive the truck like grandpa. The engine bay, chassis and body look like the truck is 2 years old, not 7. Its my 3rd Tundra and 13th Toyota overall and really never had an issue with vac lines or bad gaskets on the intake. Im not saying it isnt possible but the likelihood of bad gaskets and seals on a 7 year old Tundra “just doesn’t feel right”. I have not replaced the fuel filter as I believe it is a in-the-tank sock style that involves dropping tank or removing truck bed. If I drop the tank, she is getting new filters AND a new fuel pump. Anyhoo, thanks again for the suggestions. You have definately got me thinking to watch some videos on vac leak detection. Good write up, thanks for taking the time!

 

One more thing....the fact that the truck is getting increasingly harder to start when warm leads me more in the direction of fuel pump and not vac lines. I am guessing that the hard starting issue when the engine is at normal temperature may be an indicator that the fuel pump is showing signs of malfunctioning when exposed to the heat of normal operating temps but is functioning fine when cold, hence the hard starting when warm.....just a guess.

As my engineer buddy likes to say “nothing causes machanical failure like extreme heat or extreme cold”

 

That could be it too and you're probably on the right track. My brother-in-law was dealing with some fuel-related starting issues on one of his vehicles and it turned out to be a weak battery oddly enough. I think he was throwing a 174 code as well, but don't quote me on that. Not sure if you've changed that one, but at 7-8 years it may be getting a little long in the tooth if it's the original.

 

BTW, don't let that age number deter you. I'm 44 and I just installed a full suspension lift by myself. If my broken, strokey ass can pull that one off you can do this!

 

I actually thought of the battery. Here is an interesting tidbit...my cheap, orange Actron (spelling?) OBDII is functioning fine but will not work with my Tundra. It pulls up some “error” bs. A friend suggested the battery may be weak so I had it tested at Wally and it tested fine.

 

Last night I spent some more time working on this lien code problem, out comes the carb cleaner....aka the poor mans vacuum leak tester, de-greaser, cleaner, electrical contact cleaner, bug repellent, bear mace all wrapped up in one neatly packaged little spray bottle, the mechanic's cure all, if you will

First, I let the engine reach normal op temp, then I slowly went around the vacuum lines spraying carb cleaner around all the vacuum lines, intake, intake manifold seal, air filter box, pvc hoses, anywhere I though might be a likely spot for a vacuum leak. My results? nothing, nada, zilch, zero, no noticeable changes to engine sound or rpm fluctuations at all. If there is a vacuum leak, dammmed if I can find it!

I am leaning more and more towards fuel filter/pump problems but I wanted to do some of the cheap and easy stuff first and spraying a $4 can of carb & choke cleaner is both easy AND cheap . Dropping the tank and installing a new fuel pump is neither cheap, nor easy.

Before I drop the tank, I will probably go ahead and replace the fuel pump ECU if I can figure out where the darned thing is located

Any other mechanics care to chime in? LOTSOFTOYS? ANYONE?

 

I don't think it's your fuel pump or filter I think Toyota had it right the 1st time to the the charcoal canister

 

The charcoal canister was related to the slowness of the tank filling issue. Toyota suggested a new charcoal canister to eliminate the slow filling of the fuel tank when, in actuality, it was not the charcoal canister at all, it was a clogged fuel tank vent line. That problem has been fixed. Right now I am dealing with lean codes and a start-ability code, poor engine performance at highway speeds and difficulty starting the truck when it is hot (normal operating temperature).

Sorry, my original post probably sounded a bit confusing.

Granny always said to use the KISS method (keep it super simple)

 

No you were clearing your 1st post let us know what comes out of it

 

Thanks Swede, I will.

It has been frustrating, to say the least

 

The carb cleaner test didn't work for me either on the BMW. I never got an idle difference no matter where I sprayed it. It doesn't necessarily rule out a vacuum leak. Doing a smoke test is a little better method, but you typically have to have enough smoke in the system to actually see it come out. Here's a really cheap way of doing that one as well as a cheap DIY smoker.

 

It involves cigar smoking, me like it already! Ha

 

Sas, pretty clever diy smoke machine. I may give that a try, seems easy enough. Thanks for the links.

 

Thought I would do an update on the lien code saga....I bought a paint can smoke machine online last week but didn't get around to working on the truck until today. I removed the air filter box from the rest of the air intake and covered the intake pipe with a rubber glove. Then I hooked the smoke machine up to the brake booster vac line. "Making smoke" with the smoke machine was pretty straight forward as the machine came with easy to understand instructions. Well....(cue up the drum roll).....My results were.....zilch. The smoke machine showed no vacuum leaks and the intake and all related vac and emissions lines seemed sealed up tight with zero leaks. In fact, I "smoked" the engine 3 separate times (can't wait for comments on that statement).... I was pretty disappointed as fixing a cracked or disconnected vacuum line would have been much more simple than the increasingly likely project of dropping the fuel tank and replacing fuel pump.

I wish this post could get more traction and other guys that have dealt with the same lean codes might chime in here....

Anyways, I will post a few pics of the epic engine smoking machine...

 

Notice those shiny, new Denso coil packs??

 

You're right, I should check the fuel pressure before just "throwing money" at the fuel pump and blindly replacing it. But at 170,XXX miles, it might be good preventative maintenance to go ahead and install a new fuel pump and strainer filter.

 

Hey sorry to bother you man I just wanted to ask you if you ever figured out your problem with the 2011 Tundra I literally have the same year truck with the same engine and I have the identical problems that you have explained in your story there and just wondering if you ended up replacing the fuel pump in if that took care of it because I had same problem with the dealership is not able to figure it out either

 

I know this is an older post and related to a 4.7L originally but I just fought this issues and figured i'd share my findings. I didn't find much when I was looking and appears this is more common than it should be...

Toyota diagnosed P0171/174 and "traction control off" on my 2015 5.7L and found it to be a bad or failing fuel pump. With that, I had 70,000 miles on it and "nothing was under warranty", or so i thought. Toyota fronted the entire cost of the fuel pump under a "specifically acknowledged problem part" warranty. Come to find out, they are openly acknowledging that it is a "short life" part (and should not be) and replaced it for free. I obviously can not speak for Toyota, but this is exactly how it played out in my experience recently.

A little back history on how it came about:
Truck was a "grocery getter" for most all it's life being my wife's vehicle. Zero issues with it. I recently took it over and bought her something else. Not a tank of gas through it, I got on it hard on my way to work. Didn't miss a beat but right after i let off the throttle, check engine light came on. I did a bit of research, cleaned MAF and throttle body, checked for other issues, cleared the codes, came back at exactly 300 miles. At that point, and not willing to throw parts at a 70,000 mile Toyota, i took it in for a diag. Glad i did...

 

Looks like I'm headed down this same road now. 2014 Tundra 5.7 with P0171, P0174, and TC codes. I am noticing a somewhat significant reduction in power when pulling a trailer. This trailer weighs less than 2000lbs. At first I attributed it to the new lift and tires (7" lift with 35's). The truth comes out when I took a trip up a long hill at a steady speed and could feel the truck, almost rhythmically, stutter or hesitate.

 

i didn't notice power loss but all signs point to the same.... I would cut to the chase and get it in to toyota for a diag. they will "charge you" $60 for it but it goes towards repairs or if it is warranty work, they wont charge you in the end. how many miles? i think toyota said they limit the warranty to 100,000 but you'll want to confirm. Best of luck and hope they fix it for free man. Let us know what you figure

 

I wish it would be covered under warranty. Unfortunately I'm right at 139K. I did install a gravity fed drag up tank and I'm wondering if some trash found its way in to the main tank and clogged/fouled the fuel filter or pump. I sprayed carb cleaner over all the vacuum hoses under the hood. I considered pulling the intake manifold and replacing the gasket. I'd also pull the fuel rail and clean all the injectors at that point. I guess I'm just bummed that I'm having these problems so soon.

 

I would still think it is just a weak fuel pump. if I had to pay out of pocket, I would have dropped the tank myself and upgraded to the higher compacity tank while I was at it... Just saying.

Unless you recently did some work under the hood i would really doubt it was actually a vacuum leak. Having the exact same codes seems it would be a fuel pump but if you are not 100% and don't want to dig in yet, maybe a diag is still a good idea? They can test your fuel pressure and air to fuel ratio. Then you will at least know exactly what to chase based on their findings.

 

I did some research today that leads me to believe its a fuel delivery issue.

Looking at my short and long term fuel trim percentages, they correlate away from a vacuum leak. The following is freeze frame data from the code.
CEL ON WITH P0171,174 CODES
RPM: 2448
MAF: 9.65 LB/M
Bank 1: STFT 0.8%
LTFT 55.5%
BANK 2: STFT 3.9%
LTFT 54.7%
However, currently it is running as follows.
CEL OFF WITH P0171, 174 CODES
RPM: 805
MAF: 0.87
BANK 1: STFT 0.0%
LTFT 14.1%
BANK 2: STFT 0.0%
LTFT 12.5%

Both upstream O2 sensors read 3.2v +/-.05 in both circumstances leading me to believe they are working properly.
I am going to clear these codes and perform another drive cycle to try and induce the codes again.