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LS troubleshooting. 2004 6.0 code help

HankScorpio

HankScorpio

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I have a 2004 Chevy 6.0L, auto, 4x4, extended cab, 2500 with a flatbed. Bought it used a year ago with 100,000 miles. Been a really good truck. It is throwing code P0171 and p0174, left and right lean condition. It also threw a MAF code twice but months apart. I replaced all 4 oxygen sensors about 2 months back, Bosch. Cleaned the MAF the first time and replaced the MAF sensor a month ago, Delphi. I can drive for days around town just fine after clearing codes. During hard acceleration or heading up big hills I am still triggering the P0171 and P0174, left and right lean condition. Running 75-80mph rural highway sometimes triggers the code but not always. Seemed like things were better after sensors for a bit but the code is coming up more often now. I live at 7200ft and often drive at 10,000ft but that seems like it would be more likely to throw a rich code if altitude was affecting oxygen content. Also has a brand new air filter. What should I check next?
 
Never a fan of throwing random parts at it without doing some basic diagnosis. Did you look at the short and long term fuel trims, or the MAF readings? Fuel pressure gage? You have to be careful what you see and believe on the internet, but if you search for those codes on YouTube there are several people that are really good at walking through the diagnostic procedures to verify what is wrong. South Main Auto and Pine Hollow Auto Diagnostics are two channels that I have learned a lot from. You don't have to get nearly as in depth as they do and have all the expensive tools, but if you spend some time researching those problems you can at least get in the right general area.
 
6.2Blazer said:
Never a fan of throwing random parts at it without doing some basic diagnosis. Did you look at the short and long term fuel trims, or the MAF readings? Fuel pressure gage? You have to be careful what you see and believe on the internet, but if you search for those codes on YouTube there are several people that are really good at walking through the diagnostic procedures to verify what is wrong. South Main Auto and Pine Hollow Auto Diagnostics are two channels that I have learned a lot from. You don't have to get nearly as in depth as they do and have all the expensive tools, but if you spend some time researching those problems you can at least get in the right general area.
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While I fully agree that the parts cannon is not the way to go I also don't mind putting a fuel pump into a 100,000 mile truck as preventative maintenance. I do have a fuel pressure gauge, what should it be reading? I am not set up for reading fuel trim and MAF, just codes.
 
I was having this exact issue with my 04 5.3 in my Jimmy, except it was accompanied with backfiring. I replaced fuel pump first and it made no change. Ended up being spark plugs.
 
rderosier said:
I was having this exact issue with my 04 5.3 in my Jimmy, except it was accompanied with backfiring. I replaced fuel pump first and it made no change. Ended up being spark plugs.
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One would think that spark plugs would have resulted in a rich condition, not lean.
 
Yeah, idk, I did fuel pump, O2 sensors, and maf. I had purchased cam and crank sensors as well. Spark plugs were toward the bottom of my list but I bought some and threw them in. Trying to pin point what it was basically gave me a list of a dozen things it could possibly be so I was just checking them off one by one...
 
rderosier said:
Yeah, idk, I did fuel pump, O2 sensors, and maf. I had purchased cam and crank sensors as well. Spark plugs were toward the bottom of my list but I bought some and threw them in. Trying to pin point what it was basically gave me a list of a dozen things it could possibly be so I was just checking them off one by one...
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I hear you. I figured starting this thread would give me some more ideas. It has. Thanks. Pulling my parts cannon out of the tool box.
 
Routine repairs piss me off. I am half way through the ProFlo install on my K5. Keep having to fix other things. I want to work on fun stuff.
 
You should see 58 psi steady on the gauge. Go for a drive with the gauge installed and see if the pressure drops when you get on it.
 
jake 03 said:
You should see 58 psi steady on the gauge. Go for a drive with the gauge installed and see if the pressure drops when you get on it.
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Thats going to be interesting with the gauge I have and the hood on. Still going to try.
 
I had a similar problem with similar vintage and new fuel pressure regulator brought trims from 20+ down to 5+ or so. Scan it.
 
Going to need a bigger cannon.
Fuel pump
Fuel regulator
Spark plugs
Temp sensor
Flux Capacitor
 
Lean fuel trim codes can be from multiple sources. Sure, the weak fuel pump will result in lean fuel trim, but when it does the fuel pressure is low enough the engine runs like crap with resulting P0300 misfire codes along with it. A vacuum leak after the MAF or a leaky exhaust manifold on both sides will cause extra oxygen to be in the exhaust for the O2 sensors to detect it.

Early LS engines can have leaks at the intake manifold, intake snorkel being loose will pull in extra air. The ECM is pretty dumb in this occasion. The O2 lean value will force the computer to keep adding fuel to overcome the lean issue. Plugs will show the fuel fouling.

Ideally instead of tossing the parts cannon at it, run the diag down. I'm not saying a 100k mile truck wouldn't need a fuel pump, but it will be really smart to get the pressure value before spending the money. If it's putting out 55-65 psi at key up and staying in that range under load it's not your issue.
 
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