P0174 - Toyota 4Runner Forum

joeforman · 10-15-2012, 12:38 PM

Hi everyone, first post but long time lurker. I am currently experiencing an issue with my 2005 4runner V6 that has 123,000 miles on it. I have a check engine light on with code P0174, I have searched and searched for fixes to this and so far have not had any luck. Here is what I have done so far:
1.) Cleaned MAF - No difference
2.) Replaced Air Filter - No difference
3.) Replaced MAF - No Difference
4.) Checked all Vacuum lines - All looked good
5.) Tested both Air/Fuel Sensors with OHM Meter both were within Toyota Specs

I should also note that the exhaust smells very rich when the truck is idling. Any help that anyone can provide would be much appreciated!

ChaosStarter · 10-15-2012, 12:58 PM

What are your long-term fuel trims like? You need a scan tool to see.

Are you blowing black smoke out the back?

What do the spark plugs look like?

<<<< · 10-15-2012, 01:16 PM

Leaky EGR Valve. Find it and replace it.

.

cabowally · 10-15-2012, 01:17 PM

There is a whole diagnostic section in the FSM on this DTC. I think it's in a sub-directory within DTC's called Testing. OR may be system specific.

This summary is for the V8. Don't think there is a whole lot of difference.

p.s. A dirty fuel filter can cause a fuel pressure problem.

.

joeforman · 10-15-2012, 01:19 PM

Not seeing any black smoke coming out the tailpipe and the bumper is not becoming covered in any residue or anything like that, just smells rich (wife says it smells like we are at a Hot Rod show). I unfortunately do not have access to a scan tool, got the code # from Auto Zone. I can pull the spark plugs when I return from this business trip, dont know why I didnt think of that earlier. I replaced them about 30k miles ago. Thank you for the reply.

Any suggestions on finding the leaking EGR?

Thanks for the chart I was following a similar one that I found when I did the search, I did not test the coolant temp sensors yet or the EFI Relay. I will have to look into testing those.

BOSMECH · 10-15-2012, 01:24 PM

Time to change the O2 sensors.
Been there done that.

ChaosStarter · 10-15-2012, 01:34 PM

Quote:

Originally Posted by <<<<

Leaky EGR Valve. Find it and replace it.

No EGR valve on this motor.

Quote:

Originally Posted by cabowally

p.s. A dirty fuel filter can cause a fuel pressure problem.

No external fuel filter on this motor. Only the 'sock' directly on the fuel pump in the tank.

PCV hose attached properly?
How long has this been happening? Any driveability issues?

joeforman · 10-15-2012, 01:48 PM

Started about 3 weeks ago, no drive ability issues. Code just came up one day, as far as I can tell there has been no real difference in MPGs either. The PCV hoses look right as per the diagram and I havent moved them since I bought the truck used. Its been really throwing me so far, everything I have tested has came back normal. Thanks to everyone who has replied so far!!

BOSMECH · 10-15-2012, 03:02 PM

Quote:

Originally Posted by BOSMECH

Time to change the O2 sensors.
Been there done that.

Repete

joeforman · 10-15-2012, 03:09 PM

Are you recommending replacing all 4 O2 sensors?

BOSMECH · 10-16-2012, 09:53 AM

Yes I would because I did my left bank 1 and 2 and then about 4 days later the right bank went. So just save your self the hassel and do them all, dont forget to run a thread chasser in the pipe threads before you install them with anti sieze compound.

<<<< · 10-16-2012, 10:57 AM

My dealer suggested new fuel cap first. Not sure how it can help, but it's cheap and may be worth to try.

BOSMECH · 08-07-2013, 12:31 PM

I just got the P0174 and I think it is the gas cap since I checked everything else and the O2 sensors are all good and it only happens after my wife fills up the tank, and she does make sure the cap is tight but it comes loose real easy.

ebg18t · 08-07-2013, 12:55 PM

Quote:

Originally Posted by <<<<

My dealer suggested new fuel cap first. Not sure how it can help, but it's cheap and may be worth to try.

That is what mine was. The o-ring on the cap had deteriorated and it wasn't holding the proper pressure in the tank. Almost as if the cap was not clicked when I put it on. New cap solved the problem.

BOSMECH · 08-07-2013, 04:10 PM

Quote:

Originally Posted by ebg18t

That is what mine was. The o-ring on the cap had deteriorated and it wasn't holding the proper pressure in the tank. Almost as if the cap was not clicked when I put it on. New cap solved the problem.

I am glad that you said that because this is driving me nuts, how much was the cap from Toyota.

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