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Gm Tech (Cam)
Gm Tech (Cam), Cadillac Mechanic
Category: Cadillac
Satisfied Customers: 29427
Experience:  GM Grand Master Technician 2007. 14 years experience.
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P0171 and p0174 codes both banks to lean

Customer Question

p0171 and p0174 codes both banks to lean
Submitted: 1 year ago.
Category: Cadillac
Expert:  Gm Tech (Cam) replied 1 year ago.

Hi there, I am Cam.

To be perfectly honest, those 2 codes are almost ALWAYS due to a fuel supply issue. Usually it’s a plugged fuel filter that leads to premature failure and weakening of the fuel pump itself.
The test is to check fuel pressure. I am not sure what year your trucks, but with the 5.7 its 60-66 psi, and the 5.3 and 6.0L, its 55-62 psi.

To answer your question about the smoke, I need to know what year your truck is so I can know what engine is in it.

Customer: replied 1 year ago.

its around 49psi at idle but you can hear the pump and it sounds like it is working hard should i drive it and check it

the other thing is my long term fuel trim stays at 25

Expert:  Gm Tech (Cam) replied 1 year ago.

49 is low irregardless of which year it is. Your put a filter in so that means your fuel pump is weak.

You will need to replace the fuel pump .

Customer: replied 1 year ago.

its a 2003 6.0 what about the fuel trim stuck at 25?

Expert:  Gm Tech (Cam) replied 1 year ago.

Yes, that’s the computer trying to compensate for the lower fuel pressure by adding trim to give the engine more fuel.

Customer: replied 1 year ago.

thank you for being so prompt i will try that and let you know what happens

Expert:  Gm Tech (Cam) replied 1 year ago.

Thank you for allowing me to assist you. Please rate my answer OK to Excellent service and feel free to ask any follow up questions regarding this issue you may have.
Please know that the only compensation for my time spent assisting you is when you provide that rating.

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