2004 Denali 6.0L throwing Codes P0174, P0171, P0101, P0446

[HiHoeSilver]

Update: Used buddies non-leaking pressure gauge, 48 psi with key on but holds steady, and when started it jumps up to 58 and stays right there, whether at idle or revving the engine up. I am going to replace the air filter and fuel filter both, but I don't think that is going to fix my lean condition. I think it's time to check the intake bolts and look for an intake leak. I will also check the other things you all just talked about, I appreciate it. More updates to follow as I will have some time to work on it this weekend. Thanks.

Jeremy

Did you clear the codes?

 

[afpj]

Did you check fuel trims at idle, and at around 2000 rpm? Oxygen sensor voltage graph/pattern?

 

[BlueCollarTahoe]

i had a similar issue but running rich...turned out to be the Oxy sensors.

 

[Marinevet]

That makes sense to me. Where is the evap purge solenoid located on the truck, and is there any way to test it, or should I just replace it? I already blew off the MAF sensor, so I will check the evap purge solenoid next. I didn't get to the Yukon this weekend, I hope to either tonight or tomorrow night. Thanks again for the help.

 

[Marinevet]

Did you clear the codes?

I didn't clear them yet, I want to get the new air filter and fuel filter in first, but I didn't get to it this weekend quite yet.

Did you check fuel trims at idle, and at around 2000 rpm? Oxygen sensor voltage graph/pattern?

I am not able to check that stuff, I just have a code reader, not an actual scan tool. I don't mind paying someone to hook one up, but first I want to rule out all the things I can check myself without the scan tool.

Thanks again for all the input everyone.

Jeremy

 

[MidwestMike]

To be honest I haven't played with my newer Tahoe, but I bought a cheap bluetooth scanner that you use with your phone and Torque or some similar app.
On my last one it surprised me how much data was available. I originally bought it to try to work on towing mileage.

https://www.amazon.com/s/ref=nb_sb_...fix=OBD2+bl,automotive,227&crid=2L70ZZGVK6S0U

 

[Rocket Man]

I believe fuel pressure should be around 58 and no drop in pressure.(maybe 5lbs) we don't have a fpr on the fuel rail as it's in the tank with the pump. Sooner or later the pump will completely give out so might as well change it now and fix that evap while your down there

Actually the fpr is on the intake manifold. Don't remember exactly where but I remember removing it to reinstall on the fuel rail of my Whipple. It looks like this.

 

[Marinevet]

Actually the fpr is on the intake manifold. Don't remember exactly where but I remember removing it to reinstall on the fuel rail of my Whipple. It looks like this.

From everything I have read, this was prior to 2004. In 2004 they went to a returnless fuel system, where the regulator is actually in the gas tank.

 

[Marinevet]

To be honest I haven't played with my newer Tahoe, but I bought a cheap bluetooth scanner that you use with your phone and Torque or some similar app.
On my last one it surprised me how much data was available. I originally bought it to try to work on towing mileage.

https://www.amazon.com/s/ref=nb_sb_ss_i_3_7?url=search-alias=automotive&field-keywords=obd2+bluetooth+scanner&sprefix=OBD2+bl,automotive,227&crid=2L70ZZGVK6S0U

Do you remember which one you actually ended up buying? Those are cheaper than I thought they might be.

 

[Rocket Man]

From everything I have read, this was prior to 2004. In 2004 they went to a returnless fuel system, where the regulator is actually in the gas tank.

According to Rock Auto that one in the picture is for a 2004 but they could be wrong.