Codes P0171 and P0174, EVAP monitor not set?

KFLYNN702

MEMBER
2003 LEXUS ES 300
3.6L
V6
2WD
AUTOMATIC
209,000 MILES

Check engine codes p0171, p0174, mass air flow brand new, checked vacuum hoses, changed air filter. Evap monitor shows incomplete after drive cycle, it's the only monitor left.

Saturday, November 16th, 2024 AT 1:44 PM

4 Replies

JACOBANDNICKOLAS

MECHANIC
109,874 POSTS

Hi,

How many miles was it driven? It may still be in process. Also, if you cleared the codes, did it return? If not, then continue driving it. If there is a problem, the engine light and code should return.

Let me know.

Joe

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Saturday, November 16th, 2024 AT 7:27 PM

KFLYNN702

MEMBER
3 POSTS

After I cleared codes did about 130 miles, check engine came on after shutting down and restarting.

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Saturday, November 16th, 2024 AT 8:36 PM

KFLYNN702

MEMBER
3 POSTS

It was the PCV valve hose, had a crack in it. I didn't even know it was there.

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Sunday, November 17th, 2024 AT 7:47 PM

JACOBANDNICKOLAS

MECHANIC
109,874 POSTS

Hi,

If the light has returned, the issue isn't resolved. A lean fuel mixture can also result from a weak fuel pump. Have you checked the fuel pressure?

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Let me know. Also, let me know if these are the only two codes you have experienced. Just a couple of other questions. You indicated there are no engine vacuum leaks. Are there any exhaust leaks pre-catalytic converter? Are there any misfire issues that could indicate a fuel injector issue?

Let me know. Also, I attached the manufacturer's fuel pressure specifications below. They include the manufacturer's pressure specifications.

Let me know what you find.

Take care,

Joe

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