Ok, the codes P0171 and P0174 are a indication of a lean condition on both banks. the two most common problems for this is a weak fuel pump or a intake gasket leaking vacuum. normally with a weak fuel pump you will have a hard to start condition also, but still would be a good idea to make sure the fuel pressure is ok. if the fuel pressure is ok, then more than likely the intake gasket is leaking vacuum causing a lean condition. which is real common on these trucks. you can check the intake gasket for a vac. leak, by spraying some carb cleaner around the intake where it meets the head. if the rpm changes, then the intake gasket is leaking.
your engine code is the 8 digit from the left on your vin number. being flex fuel vehicle yours should be a Z engine.
(55-62 psi) VIN: (V, T,U)
335-375 (48-54 psi) VIN: Z
If there is anything you dont understand, please feel free to ask me to explain
yes, you can get one at autozone. being that it is a intermittent problem, the computer can make some adjustments for a lean condition, but when the computer trips codes P0171 and P0174 it is at max. the engine is just to lean to run properly. the intake gasket is a fairly easy job on this truck, depending on the shop rate in your area is, 150.00 to 250.00 in labor and the intake gasket runs
pressure is low for sure. these trucks are real critical. yes a fuel pump replacement is in order. the pump just doesnt have enough pressure to maintain proper fuel trims, causing the codes P0171 and P0174
there are some cheaper aftermarket pumps out there. but they just done seem to work as well. have seen some of these go out shortly after replacing. if you plan on keeping the vehicle long term, then the GM pump is the way to go. if you think a trade is in the near future, then a aftermarket pump would be ok and normally are half the cost
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