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I have a 2001 GMC Yukon Denali and this morning it began…

Customer Question
Hello My name is*****...

Hello My name is***** have a 2001 GMC Yukon Denali and this morning it began driving horribly. The CEL flashed and it stumbled and could barely maintain 50 MPH. I stopped at Autozone to have the CEL checked. It was throwing codes P0171, P0174, P0430, P0300 and P0706.

Mechanic's Assistant: Thanks. Can you give me any more details about your issue?

I know I attempted to add oil to it a couple days ago and spilled quite a bit on my attempt. The engine stumbles and feels like it wants to stall. Going up hills was a major struggle.

Submitted: 2 years ago.Category: GMC
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Customer reply replied 2 years ago
Its also throwing code P1810 and P1125. Please help...
Answered in 24 minutes by:
1/29/2016
GMC Mechanic: Dave Nova, GMC Technician replied 2 years ago
Dave Nova
Dave Nova, GMC Technician
Category: GMC
Satisfied Customers: 19,452
Experience: ASE Master Certification. GM World Class Certification
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Did you clear the codes to see which ones would return?

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Customer reply replied 2 years ago
No, took it back home and had to take my other vehicle.
GMC Mechanic: Dave Nova, GMC Technician replied 2 years ago

Did the engine feel like it was misfiring, or was it just a general loss of power?

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Customer reply replied 2 years ago
It was misfiring. The truck struggled going up hills and would not travel faster than 50mph.
GMC Mechanic: Dave Nova, GMC Technician replied 2 years ago

With the codes you have, p0171 and P0174 are lean codes and P0300 is a misfire code. Sounds like the engine is starving for fuel. If you have not replaced the fuel filter in a while, I'd start there. Beyond that, testing fuel pressure will reveal whether the fuel pump needs to be replaced. You should have 60-66 psi fuel pressure with the key on, engine off. If the fuel pressure is lower than specified, the fuel pump should be replaced.

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