Resolved: Check Eng Light w/P0171 & P0174

EDIT - resolution: consensus was since the codes were for both banks that it was either gonna be the fuel pump or the mass airflow.

Cleaned the mass airflow no luck.
Tested the fuel pump. It was fine.
Replaced the master airflow - problem resolved.


ORIG:

Couldn't even get home from the shop to enjoy getting my alignment, having the steering rack completed, having it raised 1 inch in the front, getting the TPMS replaced because the shop would not use Denso from the start, and getting new complete drive shaft with three new U joints and a new carrier bearing

and I've got these two codes


I've already read the basics. I'll start researching it later.

 

This was my favorite P0171 case: https://www.tundras.com/posts/2800368/

But in all seriousness, "too lean" is potentially a lack of fuel delivery. Your fuel pump is quite probably taking a shit, given it's lean on both banks, knowing the '05-'06 don't have a fuel filter that could be impeding things, and I'm pretty sure the pressure regulators are on each respective rail (thus wouldn't fail at same time). Depending on whether Denso has inventory, you may need to buy the OEM part. Not a fun job, but if you go OEM/Denso, you shouldn't need to do it for another 15+ years.

 

Yeah, I've already used that thread title edit option after searching way too long to find it, but thanks!

Yeah, once I read the list of probable causes, I suspected the fuel pump because I was getting these codes for almost 2 years when I wasn't doing maintenance or involved in the selection.

And it turned out it was the fuel pump. My first shop couldn't diagnose it for two years. Then the second shop replaced it, but they were the ones that if you recall put those cheap shit swaybar links on it so they probably used the cheap fuel pump as well


I'm not gonna put all the blame on them because I really thought my truck was getting close to end of life And told them Not to use the most expensive parts. Fortunately, I believe this only occurred with those swaybar links and the fuel pump

I remember they said it was getting codes for running lean etc, but I do not recall the check engine light coming on. I only recall that if you sat there with it idling in the middle of the summer for an extended period of time it would idle very rough and when you would takeoff it sputter and then eventually after a few hundred feet run smooth.

I'm almost positive it wasn't triggering the check engine light or I would've been more concerned. But it could be wrong. Nevertheless, here we are.


1st peak at OEM:



After a little More searching it appears around 450 is the going rate for OEM but I'm still searching

 

Denso is this cheap? Doesn't seem right after looking at the other aftermarket products. Picture doesn't look right, but the description sounds correct

 

Yup, that's about right.

I always cross-reference my part numbers using the part lookup tool @ www.densoautoparts.com

Once I have the part number, I'll run it thru RockAuto and Summit Racing to see who's got it cheaper after tax and shipping, and execute.

 

Well, that's not bad at all

 

But before I get too far, I should probably check a couple of other possible causes

 

where is that sensor in or around the tank located? There's a reason I ask

 

so you dont think it could be the MAF?

 

Sensor for what? Is there a tank pressure sensor on our later-year trucks? I know my last truck had one, it'll throw evap codes when it does?

I mean ... do you still have your old one? If I'm ever replacing parts and I'm not convinced the old part is bad, I keep it. Makes it really easy to swap the old one back in.

You're not using an SAIS bypass kit, are you?

 

I was referring to that Link you sent for that thread related to one person's experience with these codes.

I am not using the bybass kit

The old part? Are you talking about the fuel pump? I would say that true to your suggestion the original lasted 15 years and I'm sure it was bad. And based on the history, I'm sure they did not use OEM or Denso so it doesn't surprise me it is a problem now

And I'm only now learning to keep many of the things I'm either replacing or removing

 

I'll go back and read. A little slow getting into it today. 5mi hike with the kids yesterday followed by a 10mi out and back on a rocky path with the oldest, I was late to get up and the coffee isn't kicking in fast enough.

EDIT: Ah - no, their issue was the pickup hose was loose. Twice.

MAF. I thought you said you replaced the MAF at some point, and you were asking about the MAF. If you have a DMM, you can measure resistance on the MAF to verify operation. Process is in the FSM, but I know BubbaW and a couple others have posted a screencap of the process on here a few times.

Some folks on here would holler at you for it. "It's taking up space!" But I like keeping things like that laying around for sake of troubleshooting later, if I'm not 100% positive they were the source. With the MAF, I'd have tested it using FSM process before pulling/replacing. If clearly out of spec - understanding the resistance you'll see will go up or down depending on the ambient outside temperature - I'd replace and probably toss the old.

 

I understand. When I posted a lot of this, I was worn out yesterday and it was getting late.

No, I did not replace MAF - only the fuel pump. I just know when I did a quick search on the two codes I'm now getting that was one of the possible causes.

And yes, I ran into the first issue of needing the old parts when I got that support off of the old grill. Thankfully, I still have the old grill. I know there was another instance for a different old replaced part But after that, I knew I needed to the save old parts when reasonable

 

Which reminds me, I still have this fully assembled white grille (minus Toyota emblem) For the 2005-2006 I need to do something with. They take up a lot of space.

Anyway, from the FSM, testing the resistance on the MAF process. 1st pic is for the '05-'06 V8 but I'm also dropping the 2nd pic for the V6 in case someone with the V6 stumbles upon this later. Note the graph that gives you the approximate resistance range based on temp.

For the V8 / 2UZ-FE:

​

For the V6 / 1GR-FE:

​

​

 

Shifty, thanks. That is great info on troubleshooting the MAF. I Should be able to do that in the next few days

my new shop, who has mostly been great with a few relatively minor exceptions, replace that fuel pump and he's tracking down what brand they used because it was Four years ago. He also thinks they might be able to get a credit on it if it is in fact, failing that could essentially make a new Denso practically free



speaking of Denso my only concern with that price I got is the Denso does not have as many parts as the OEM or others I've seen online. Now I recognize lots of times they use stock pictures that may not be accurate but the Denso that I found that is supposed to fit just looks much simpler


Denso:



OEM or similar:

 

Stock images are not always correct.

Additionally, what you're seeing is in the 2nd pic is a fuel pump assembly. The 1st pic it just the pump, where you'd pull the assembly, remove the pump from the assembly, then install the assembly.

I haven't done this job specifically on a 1st gen Tundra, but I've installed my fair share of fuel pumps, both replacing OEM, and into aluminum fuel cells (usually Walbro, they make a great pump), and the little cylinder is the actual pump-pump.

Will you get the full assembly if you order OEM? I am not sure. But the only time you really need to replace the assembly is if the sender is flaky, i.e. you've got a dead spot in the float/slide that sends resistance back to the gas gauge.

It looks like the part number you pulled truly is the valid part for your truck. If you want to replace the whole assembly, OEM may be the way. You'll be forking out some coin though.

​

 

PS the fuel pump stuff for my '06 is here, the assembly (with sender) p/n is 77020-0C061, which is the part you're showing in the 2nd pic: https://toyota-usa.epc-data.com/tundra/uck40/3806/body/7751/

It looks like the sender alongfor our trucks is 83320-0C011 (posting that info for me, for future ref). https://toyota-usa.epc-data.com/tundra/uck40/3806/body/8401/

It's really up to you whether you want to replace the entire assembly or just the pump, I guess.

 

consensus was since the codes were for both banks that it was most likely either gonna be the fuel pump or the mass airflow.

Cleaned the mass airflow no luck.
Tested the fuel pump. It was fine.
I didn't bother to test the mass airflow. I just replaced it - problem resolved.

thanks for all the input everyone