1999 GMC Yukon P0174

CPAYNTER2

MEMBER
1999 GMC YUKON
V8
4WD
AUTOMATIC
89,764 MILES

I have a MIL active showing a troublecode of P174. In using the online troubleshooter on my OBD II scanner it tells me either low fuel pressure or vaccum leaks. The fuel pump and filter were replaced at the onset of the MIL I have checked for vaccum leaks and don't see any, I checked with a vaccum tester. There are only two vaccum ports I can see, one for the brake booster and the other for the HVAC vent controls. Have you seen the problem before and do you have any suggestions. Thank you,
Chuck

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

P0174

A lean fuel condition

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)

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Friday, May 1st, 2009 AT 6:36 PM

CPAYNTER2

MEMBER
3 POSTS

I have checked fuel pressure, vacuum tested the hose connections as well as sprayed carb cleaner around all hose connections, EGR valve, and intake manifold. Would dirty injectors cause this problem and wouldn't a dirty or defective MAF generate it's own trouble code. Have you run across this problem before and if so what was the cause of failure?
Thank you.

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Friday, May 1st, 2009 AT 6:52 PM

RASMATAZ

MECHANIC
75,992 POSTS

I have checked fuel pressure

What was the actual fuel pressure when you check it? You need to check it one by one -I've given you all I got on lean condition, If all checks out-could be coming from the computer itself

Try rescanning the computer and see what else is in there

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Friday, May 1st, 2009 AT 7:26 PM