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 Show 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.