I bought an OEM cap off amazon for $15-20.

I initially blamed my wife for not tightening it properly when she filled up. Then it did it to me. I never told her I replaced the cap... LOL.

Good recovery.

in the same boat, long tern fuel trims high 35%, p0174 code. cleaned maf+TB, no change.02 sensor reading are ok from the scan tool. really stumped!

bought a fuel pressure kit and fuel cap from amazon, will check my fuel supply pressure and try to eliminate possible causes

Hopefully it’s as simple as the cap! Unfortunately, I’ve never been that lucky when it comes to CELs...

so this was a permanent solution?, replacing the gas cap. i have a stubborn p0174 and its driving me nuts

I got the P0174 code. It's come on and gone off a couple of times. Usually comes on after I have to do a fast acceleration (which with 186K miles isn't all that fast anymore). I recently filled up and the light went off which makes me think it is the gas cap, though I haven't noticed any deterioration.

still dont understand how a bad gas cap will only affect bank 2, hence the p0174, i was thinking it should affect both banks, hence it would throw a p0171 code as well

@BOSMECH , so seems you changed your o2 sensors and it didnt resolve the problem?, ,......what did the gas cap change?

Did you ever get this figured out? chasing bank 2 lean codes. they keep changing. p0158, p0174, p2197

Yup i did.
My fuel trims got worse.upto 39% for bank 2 and 20% for bank 1 and occasinal p171 &p0430
I bought remanned injectors off ebay for 59 bucks and swapped. All codes went away and my fuel trims are great now, abt -2 or so..
See pic of old vs new injectors

Thanks for the reply. Mine was a little more weird, that I think I narrowed down.

Just recently bought a 2006 v8 4wd with a blown engine to compliment my supercharged 03. Installed the engine, fixed the MAF connector, and the codes started. So today, I swapped the upstream o2 banks and the code followed. So I installed the denso replacement and I got from amazon, and the code was still there. Swapped the new one back to the original troubled bank, and the code followed back. Only conclusion is that it is DOA and I actually think it’s counterfeit because the box is a different color and looks cheaply printed compared to the downstream denso replacement box

Posting my solution, in case it helps anybody in the future: After trying 2 new sensors and seeing that the code was following the bank, I decided to replace both upstream sensors. I cleared the codes one more time, and it now seems that the code is gone for now, for good. LTFT are perfect on both banks. It seems that the ECU wants to see the both side replaced at the same time, as probably a good old sensor vs a good new sensor has too large of a voltage or resistance discrepancy. It likely compares both banks to throw the code.

Now, all is good. I did use 2 Denso amazon replacements. This Harbor Freight Wrench set is probably the easiest way to get these off. Makes it a 5 minute job on each side with a cold engine.

Metric Double-End Flare Nut Wrench Set, 5 Pc.