Still battling P0174

I posted previously the exhaust system on my new-to-me ’07 Sequoia is a crime scene, with aftermarket cats and the down tubes welded to the exhaust manifolds.

I'm still fighting with the P0174. The P0430 comes and goes... I did most of the things suggested in another post about the P0174. I put in new spark plugs, cleaned the MAF and throttle body, replaced the PCV valve and the hose to the valve, replaced the hose from the air box to the regulator on the passenger side, and did a couple of other things.

Unfortunately, the P0174 keeps popping up. The upstream Bank 2 sensor was marked Denso Toyota. I suppose it could be the original. So I replaced it with a new Denso Direct Fit unit.

No change. I still get the P0174, but I'm not getting the 420/430.

What should I try next?

Thanks,

 

Do you have access to a scan tool with data?

 

Have you opened the factory service manual and looked in there for the troubleshooting workflow on P0174?

 

after hunting al over for th cause of my p0171 and p0174, changing all the seals on the fuel injectors was eventually my culprit. i started at the least labor intensive and that was the hardest so it was the last( maf cleaning, pcv change, fuel filter change, replacing very minor-ly cracked hoses(just on the tips they were starting)


matt

 

Yeah, they bought a Autel MX808S back in Mar when they were dealing with the same P0174 and other things where showing us some Live Data was mentioned.

Dreaded TRAC OFF and VSC TRAC and Check Engine Lights | Toyota Tundra Forum

Another hose question


@poormxdad , with that new Autel, if you could post certain Live Data findings, especially the ones below, it might give us an idea of what's going on. Be sure to have your SEQ properly warm and take the readings in Idle.

You may know this by now but when you're reading Live Data with the Autel, you can place a check mark next to items of interest and then select Existing down on the task bar. Take a screen shot and post results.

 

I too had those codes. Changed the fuel filter, maf sensor, and plugs with no improvement. It ended up being gunked up fuel injectors.

 

Gents,

I do have the Autel, and I'm still learning how to use it. I've played with the Live Data function, but can't seem to get anything to display.

shifty,

I don't have an FSM. However, you posted what I needed to do, and I've done the easiest things first. I have NOT yet replaced the fuel filter. I'll try to get that done soonest.

 

If you have questions of what’s needed to make it display live data, ask away. Numerous members here have Autel.

 

Go to the Megathread. "So you just bought a 1st gen" in the sticky thread list. 5th line, I think? Service manual link. Get the one for 05-06 tundra. Same engine. Same diagnostic path, I'm assuming.

They stopped using fuel filters after 2004. 05+ shouldn't have one, not even in Sequoia.

 

How did you figure that out?

 

Well, I didn’t. After throwing parts at it (outside of any O2 sensors), I didn’t want to keep doing that. So, I’m fortunate enough to have a great relationship with a local dealer who diagnosed it. They just ran Techron through it (a lot) which remedied the issue.

 

Gents,

I replaced the hose with the red line drawn on it with a new, OEM hose.



Steering is noticeably lighter. The engine seems smoother. Honest.

I've only put a handful of miles on it since replacing the hose, but I was wondering... if the hose was deteriorated enough to affect steering performance, could it be the cause of the P0174?

Thanks,

 

It was mentioned in your other thread asking about those 2 hoses. The fittings they both are attached to have manifold vacuum with
engine running. The one you replaced is Bank 2.

As for your P0174 question, I’ll let google AI answer that for you….



Now that you have fixed the possible vacuum leak, suggest you unhook battery for about 30 min. Once you hook it back up, the ECU will perform a re-learn. Your Seq might run even smoother.

 

Good call. I've done as you suggested.

What's the proper way to allow the ECU relearn? I've just been letting her sit until the idle settles out, then I take her around my little town. Should I include some highway time?

Thanks much,

 

A proper drive cycle on most vehicles involves traveling at lower speeds, traveling at higher speeds, stop-and go, and sometimes two or three starts or a mileage/time component. Idling usually won’t satisfy, but you may still pop a code before relearn completes.

 

How long does the process take? Should I start driving before the idle settles out?

Thanks!

 

If it were me. I’d go drive 5-10 minutes of surface streets to an interstate, 10-15 minutes on the interstate, and 5-10 minutes home on surface streets if that’s doable for you.

 

shifty,

I did basically as you suggested. Did some hard accelerations, too, and got her up in the 90 mph range. Drove her for more than half an hour and no codes. We'll see what happens today...

 

If you have a scanner/reader, you should be able to check the readiness with it. I think most (even cheap ones) support it, although it may not be obvious what it is.

 

Getting frustrated now…

I mentioned replacing the hose in the pic in Post #12 above and how the steering got lighter. She ran smoother. I went several days without a CEL, but then the P0174 came back. I replaced the sister hose to the one for the steering assist (Post #12) and thought I’d conquered it. But noooooooooooooooooooooooooooo. I would get several days’ worth of driving to and from work and such, but it would eventually come back.

I installed a set of the 12-hole injectors. I honestly believe she runs even better than before, but now the P0174 pops up within just a few miles after clearing it.

To recap… new iridium plugs, new air filter, I’ve cleaned the MAF and TB, replaced the PCV valve and hose and most of the evap hoses, replaced a bunch of vacuum hose, and the new injectors. I’ve run four bottles of Techron through her.

What next?

 

As it should, any time you replace all injectors after 100k-150k+ miles you're probably going to see a noteworthy improvement in function.

Did you mention prior that you'd replaced the upstream O2/air-fuel ratio sensor on passenger side? If not, have you looked at the short term and long term fuel trims for both banks? That sensor is what's helping report #s to the ECU so it can adjust trims.

Any evidence of intake/exhaust leak on bank 2?

I seem to recall mention of a specific way to stack washers on the fuel rail of one bank or the other, I'm not sure if it could lead to this, but just throwing shit at a wall, maybe it'll stick?

But ultimately, "too lean" for an entire bank, not just a single cylinder ... only a few possible causes:

• There's a problem with fuel delivery to that entire fuel rail
  • Could be a vacuum hose problem, or incorrectly attached hoses, wrong hose used so it's collapsing ... like, if the vacuum hose from the fuel damper/regulator on the passenger rail wasn't connected, and vacuum wasn't opening the regulator enough, you'd get insufficient fuel to the entire rail
  • Could be a problem at the bridge between the bank 1 and bank 2 rails
• Air leak, i.e. you're getting too much air on the entire bank, thus the amount of fuel being sprayed into the cylinders is insufficient in ratio to the air
  • Intake gasket leak, but would be wierd for a breach along all cylinders IMHO
  • Intake not properly seated/bolted down on passenger side
• Exhaust leak, i.e. you have...
  • Gasses escaping from the combustion stream before the sensor reads it (this is a stretch and possibly not true)
  • Breach exhaust flange from exhaust to cat
  • Some other issue, like improperly seated upstream sensor
• There's a problem with ECU reading fuel/air ratio
  • Bad upstream sensor
  • Poorly seated upstream sensor?

It would really help if you had a basic code reader that can tell you fuel trim data, I guess. So we can see what the ECU thinks it's needing to spray.

 

shifty,

I did replace the upstream sensor on the right bank. It had a Denso sensor that said Toyota on it. I made the assumption it was an original, and replaced it with a new Denso.

You may recall she was the victim of catalytic converter theft, and some complete a-hole welded the down tubes to the exhaust manifolds. The exhaust system is a mess.

I have an Autel MX808 scanner. It does all kinds of shit I have yet to figure out. How would I go about checking the fuel trims?

Thanks much,

 

I'll repost what I did a month 1/2 ago about Fuel Trims and what not back in Post # 5....

Can you get to the menu page where it shows Live Data like shown in 1st pic below....puzzled that you can play with Live Data but nothing displays.

If you can get to actual Live Data selection(pic 1), select Live Data, then place a check next to the items I've shown(pic 2), then select Existing down at bottom task bar.

You should then see Live Data of only items you selected(pic 3)....take pic and upload to this thread.
As a side not....MAF reading wouldn't fit as a selection but if you can get Live Data of MAF reading it would be great.

Don't mind my readings....it's 105 here and didn't linger long outside.

 

I actually don't remember. So many threads get posted, and you keep posting new threads, which makes it impossible for me to keep up in a linear fashion. You've done yourself a huge misservice creating several new threads on the same topic, so I'm glad to see this one has stuck around for a few weeks. You deserve kudos for that. (no sarcasm here!)

Bubba covered it! Listen to him! He always provides sage advice.

 

Apologies. I only got the fuel trims and engine speed, but I wanted to post it anyway. I'll take another stab at it.

I didn't go out of my little town.

Does this provide any insight? Do I need to drive around, or do we just need a reading at idle?



Thanks much,

 

This is why fuel trim data is key. Although you are throwing a P0174, which indicates the issue is limited to just one bank, the actual issue is affecting both banks. It's JUST not quite enough to hit the threshold for a P0171 on bank one. Really need readings at idle and at around 2500 rpm if stationary. Not enough load otherwise.

 

@poormxdad in one of your prior threads, did you ever mention checking the fuel pressure or replacing the fuel pump?

(note: this is why it's kinda important to keep all info regarding an issue in a single thread, so we have reference data to work with)

 

I have done neither. As Fragman hinted at above, I assumed since it was one bank that the fuel pump was not the issue.

Can the Autel scanner read fuel pressure?

 

I can probably get those readings done here shortly if I can do it without moving. Traffic is complete shit right now anyplace where I can get up some speed.

 

As I mentioned a few posts up and back in May..... "Be sure to have your SEQ properly warm and take the readings in Idle".

I also agree with @Fragman and 2500 RPM suggestion. You don't need to drive around for those readings, simply in Park will do. Upload picture of what is on the Autel screen instead of spreadsheet would be best.

Posting the items mentioned earlier would help tremendously instead of us bouncing back and forth with a tidbit here and tidbit there.