P0171 P0174: Those pesky lean codes!!!

i bet it comes back at 300miles. on a positive note, i did gain 2mpg after the new fuel pump...

 

Yesterday the codes came back on and i checked as soon as they did. My LTFT was 34.9 on both banks but dropped on acceleration. I ordered a new MAF in response to what I saw. Its not too expensive and it's super easy to swap. I'm only doing this because I can't find any parameters for the acceptable ranges for the MAF. At idle, I'm sitting at 6.26 gr/s at703 rpm and jumping to 28.46 gr/s at 3000 rpm. Part comes in today. I will update shortly.

 

Any MPG improvement is worth a shout out!! I love my truck almost as much as my company fuel card!! I'm averaging 9.4 mpg.... I also cover 500-800 miles a week.

 

New MAF, same situation...

 

Bummer

 

Fuel pump man...!

 

Yeah. Did you go with oem or aftermarket?

 

I tend to go with OEM. The dealer wants $525 for the fuel pump when I can get it after market for about half of that.

 

it was all warranty work at Toyota so it was OEM. i would go with OEM for sure and make sure it is the upgraded part number as well. not the old part number that just failed on you.

 

Fuel pump is ordered and will be here tomorrow. I will update every one as soon as I know that this solved the problem.

 

Sweet! good luck and i hope all goes well

 

So, I felt it was necessary to update this with my findings for future diagnostics. I tested the fuel pressure and got 38 psi on start and within 5 seconds, it dropped to 25-27 psi. I also did a volume test and got very little. This is what I used to confirm the fuel pump was failing.

 

@RaptorBronco do you have any details on the fuel pump replacement? I am also in a 2015 5.7L and just got the same error codes... Just looking for a recall number or bulletin number or something. Thank you!

 

i don't know that it's a "recall" at all. Toyota just told me it is an "extended warranty part that Toyota recognizes has a short life and replaces/upgrades it at no cost, up to 100,000miles". I was shocked not to find more details on it here. that is why bumped this one with more info. sorry I don't have a ton of info. all i can say is don't waste your time. Take it in for diag and get it replaced if it is the same codes and same situation as mine. and sounds like @Scutterborn as well...

Keep us posted on what they say. Seems to be a good bit of value from this thread and this common problem.

 

@RaptorBronco word, thank you. Mine is at 120k miles... I'll go ahead and get it diagnosed & just swap it myself if it's bad.

 

The following info is from my Toyota invoice 3/4/2021. @xround had a good point about listing part numbers.

1 --Cause/Action to Take
CEL -CUSTOMER STATES CHECK ENGINE LIGHT IS ON. CHECK AND ADVISE. lean codes on bank 1 and bank 2 found p0171 p0174. found tsb related to these codes. parts ordered.
1 --Correction/Action Taken
followed procedures for T-SB-0166-19, recalibrated ecu, installed fuel pump, reset learning, reset alchol fuel density learning, added 3 gallons. test drove. vehilce has no codes and is working properly.

op code EG1904

1-07 t2-74
Part numbers:
770200C120 Tube Assy, Fuel Suct
771690C010 Gasket, Fuel Suction

 

Fuel pump is installed and everything is working as it should be. No more codes or hesitation.

 

Sweet!!!

 

Got the tank dropped and discovered I have a Flexfuel Tundra. Epic!

Also the check engine light has been off for about 100 miles now. After reassembly, I did some more research and some have had the same P0171/P0174 codes resolved with a Techstream reset of the fuel computer on the FFV engines. Guess I'm going to try that next. Will post results.

 

Any good news yet?

 

Haven’t made it to Toyota yet. CEL still isn’t on. After getting the fuel tank on I also swapped the throttle body gasket from the factory mesh to a new supple OEM non-mesh one. I did it to eliminate the high pitch whistle issue, but I guess it could have something to do with creating a Lean condition if the old one wasn’t providing a good seal.

I’ll be sure to update the thread once I have Toyota take a look at it.

 

Quick update, I decided to take the truck to Toyota after towing a light boat & getting very bad throttle hesitation & CEL came back on. According to them my fuel pump was junk, the fuel trim was going wild because of this, and it also impacted my transmission learning. They installed new fuel pump, updated my transmission program, and I went ahead and had them install new spark plugs & tune up while they had it. $1400 later it drives like a different truck, very epic.

Thanks to members here for help diagnosing the issue, it made me feel better to hear from them that the problem was what I was expecting.

A note on the fuel pump: I asked if I could just buy myself a fuel pump and put it in, and he said due to the ongoing fuel pump recall, any aftermarket or OEM fuel pump I would buy outside of a Toyota dealership would be the older failure-prone fuel pump design. I don't know how much truth there is to this, but it is something to consider for the DIY-oriented. I generally always do this type of vehicle work myself but decided to play it safe here.

 

Looks like I need to start down this road! I made it to 183K though. My gas mileage has taken a dump and I get the P0171 code. Clear it and it magically appears again.
I'll have to check it after lines 1 through 9678 get checked off the ole to do list.

 

Just throwing this out there as it was my problem to the P0171/P0174. My brake booster had a vacuum leak causing my truck to run lean

 

Got em

 

Originally became a member because my '08 had the same symptoms as Broken_Taco: CEL for lean codes banks 1 (P0171) and 2 (P0174), Lo 4 light, Traction Control, sputtering and loss of power (especially uphill on highways), and difficulty idling upon restarting a warm engine (more sputtering for like 10 minutes). I'd been to two dealerships and neither could diagnose the problem...smoke test and new MAF sensor and air intake, testing ignition coils and changing spark plugs. All to no avail. So that led me to this forum, which I wish I'd discovered sooner. It's been a year now since I finally swapped out the fuel pump myself and so far no issues. Now, this is the first place I check for troubleshooting stuff and mod suggestions. This is a great community and certainly invaluable. Thanks to all who contribute and help others like myself get a handle on the problem.

 

Might come in handy for future diagnosing. Thanks