P0171 code

Truck died on the road about a week ago and had fuel problems whether air or gas. So got it home and every so often throughout the week I would start it up idle for about five minutes drop rpms and die and then every time you start it up like within 30 minutes that time would just keep dropping and it’s not the maf unplugged that no change so I’m guessing gas issue?


Likely a bad fuel injector since it only affects bank 1

I’m also thinking it could be the Ecm because I had a misfire caused by the maf so that could be fried also

Is there a particular reason you think it might be an ECM problem? Like perhaps the engine & passenger compartments both got wet etc? Or the ECM has been removed and inspected several times already? B/c removing it , if not done properly could shock-damage parts. ECM’s if left alone are usually pretty reliable, and not where to start looking for the cause of a lean code.

You might try using propane wand to find the source of a vacuum or intake manifold leak. If the engine rpm suddenly increases, there’s some sort of vacuum leak nearby. Clogged fuel injectors are tricky to find. Often its better just to try to unclog them using a fuel treatment. Replacing the fuel filter as a flyer makes sense too.

Do you have a reason to suspect you might have got some bad fuel? That would be pretty unusual for most name brand gasoline.

Your ecm can get problematic if you have a misfire like It could destroy it

I suppose it could happen, but I’d put that on the lower priorities of possibilities to consider. I mean if that’s the only reason you think you might have a bad ECM.

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Doubtful because the truck is still running. A bad ECU is a guess, not a diagnosis.

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you never said what year or engine you have.

How To Fix – Chevy Silverado P0171 Trouble Code - My Pro Street (prostreetonline.com)

Having a little trouble believing the article since the 2005 Silverado did not come with a 5.7 engine and I’ve never seen a multimeter with a Hz function. I’ve seen a lot of freq meters but never a multimeter with that function.

How to measure frequency using Multimeter - Inst Tools (instrumentationtools.com)

agree about the year. I think it was a 5.3 that year

The fuel pump is failing, measure the fuel pressure.

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@Nevada_545 is probably right. There is a YouTube video on common problems with that generation of Silverados and fuel pumps are one, and that is the failure mode when it happens. It is probably the filter that is plugged but the filter is a non replaceable part of the fuel pump. :frowning_face:

sorry keith, I was sitting here thinking about it, I hope you did not think I posted the link because I thought you did not know how to use a multimeter. it was just to show that some do have HZ. to be honest I did not know it either until I asked my son who is a electrician.

Don’t just fixate on bank 1 because you have P0171

I wouldn’t be surprised if fuel trims on bank 2 are also very high, probably not yet bad enough to set P0174