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P0171 p0174 2000 GMC Sierra 2500 6.0

  • AAron16
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4 years 2 months ago #53875 by AAron16
P0171 p0174 2000 GMC Sierra 2500 6.0 was created by AAron16
Somebody help!! I’ve got a 2000 GMC Sierra 2500 with the big 6.0.

P0171 p0174 codes pretty persistent.

I smoked the system through the fuel regulator vacuum hose and found not any smoke at all. Pcv valve, MAF, intake manifold, plugs, wires, injectors (o-rings as well ) have all been replaced and re smoked. IAC, and purge valve have been replaced. Fuel pump and filter were replaced and pressure is good.

Ltft for both banks is at 25% with no change under load.

Stft is around 8-11% at idle and goes around 0 -1% under load. ( not a fuel trim expert here )

Sorry to say that yes, that parts shotgun has been fired. If someone could give me some guidance here that be great!

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4 years 2 months ago #53876 by AAron16
Replied by AAron16 on topic P0171 p0174 2000 GMC Sierra 2500 6.0
02 sensors are also new

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  • juergen.scholl
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4 years 2 months ago - 4 years 2 months ago #53878 by juergen.scholl
Replied by juergen.scholl on topic P0171 p0174 2000 GMC Sierra 2500 6.0
If flex fuel is applicable then fuel composition sensor comes to mind, did you check it and perform a relearn?

What are the actual MAF readings, are you sure the new injectors' flow rate is the correct one?
An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 4 years 2 months ago by juergen.scholl.

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4 years 2 months ago #53881 by AAron16
Replied by AAron16 on topic P0171 p0174 2000 GMC Sierra 2500 6.0
Doesn’t have flex fuel.

MAF readings were 8-9 gps at start up and went down to about 4.7 -5.3 gps area.

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4 years 2 months ago #53892 by AAron16
Replied by AAron16 on topic P0171 p0174 2000 GMC Sierra 2500 6.0
So I unplugged MAF then started the truck

Ltft went around to 0.8%-1% area

Stft went around -10%

Could this mean anything for my MAF?

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  • Tyler
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4 years 2 months ago #53893 by Tyler
Replied by Tyler on topic P0171 p0174 2000 GMC Sierra 2500 6.0

So I unplugged MAF then started the truck

Ltft went around to 0.8%-1% area

Stft went around -10%

Could this mean anything for my MAF?

I'd want to check Calculated Load and MAF g/s during a wide open throttle run through the 1-2 shift. If the Calc Load is low and the MAF is underreporting, then you may be onto a MAF problem.

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