Not sure if this in the right section. Whenever my fuel tank depletes to more or less 1/4 of a tank I get a two P0171 lean bank 1 codes. I know the tank has to come out, I smell raw fuel just about all the time. What if anything could be in common between the fuel smell, low fuel in the tank and the codes???? I realize there is a lot of plumbing on top of the tank I just have yet to drop it and investigate anything.
2004 Yukon SLT 5.3 P0171
- Thread starter 82nd Abn
- Start date
Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.
strutaeng
Full Access Member
P0171 and P0174 are lean codes for each bank. Is that what usually are getting?
You need to hook up a fuel pressure guage when those codes are set, and ideally under driving conditions to make the determination if you have a fuel delivery issue.
Prior to even doing that, one can hook up an advance scanner and monitor the fuel trims while driving.
You need to hook up a fuel pressure guage when those codes are set, and ideally under driving conditions to make the determination if you have a fuel delivery issue.
Prior to even doing that, one can hook up an advance scanner and monitor the fuel trims while driving.
Is the engine Flex Fuel or just gas?
I am getting only one code P0171 I don't have a scanner. I smell raw fuel and when the tank gets to 1/4 the code comes on, once I fill it up the code goes away. I am pretty sure the two are related and was wondering if anyone experienced this before
Just gas
strutaeng
Full Access Member
Oh ok. Then then likely not fuel delivery issue, in spite of your observations correlating that with the fuel tank level. Those codes will often times time cause the check engine light (CEL) to illuminate on the instrument cluster intermittenly, but if you get the vehicle scanned, it will show pending and stored.
For a P0171, I would check for vacuum leaks. There PCV tubing on the intake gets brittle and cracks. It's very common. Pop the hood and try to "hear" the vacuum leak.
I highly recommend you get yourself a scanner for working on your truck. Something that reads live data and has ability to do misfire counts and bidirectional controls. But at the minimum, a $30 scanner can read CEL codes.
Good luck.
If it's running rich for a length of time it can ruin the cats, so it would be good to check deeper into the fuel trims and what the code is.
It is sitting in the garage, I have a second vehicle I am driving until I fix the yukon. I will get out there this weekend and look at the hoses. I was wondering if there was a vacuum hose that went to the fuel tank that might fix both problems
Last edited by a moderator:
- Joined
- Dec 31, 2025
- Posts
- 554
- Reaction score
- 509
Lean codes generally are saying there is extra or unmetered air being introduced in the engine after the mass air flow sensor. U can start the truck and spray brake clean around the intake area and check for leaks. Atleast that's what I do. Evap lines run from the tank to the intake to reburn fumes.. u more than likely have a air leak for it to be both banks. Just from experience.
