P0174 - Lean Bank 2 - 2017 6.2 Denali

[ShawnQ]

Good evening, folks.

Trying to get a CEL fixed, and having issues diagnosing it. The DTC is P0174...I have searched and read a TON.

The truck is a 2017 Denali, 6.2, 125k miles.

It had the injectors and intake gaskets changed about 20k miles ago, as well as AC condenser...but not likely an issue.

It seems to run fine, but my LTFT on Bank 2 is in the +20s...
I do not have an injector fault code.
I do not notice any major intake/vac leaks with the brake cleaner test.
I do not see/notice any major exhaust leaks.

The O2 sensors seem to be even on both banks, with voltages fluctuating as I'd expect...so I don't think it's an O2.
Im leaning towards a bad injector or an intake leak. Any obvious ways to verify? I would just expect a code if an injector was dead, or horrible power, or economy. Seems to run pretty good and mileage is about normal.

I was thinking about pulling plugs first and going from there...maybe one is obviously cleaner than the other. With a LTFT reading +20, I expect a major issue...but I'm only seeing that one DTC.

Thanks in advance

 

[jaxscuby]

LTFT +20...adding a bunch of fuel..do you smell gas when its running?
you would see it in mileage..and how it is running.

a coworker's silverado had something similar..but you could smell the gas when idling.
he had a stuck injector. same code, no msfire cels..

yes pull the plugs first.

use to swap injectors around to track down misfire codes on my rice burner.

but adding fuel is due to too much air...check for pinched intake manifold gasket..

 

[Rygrego]

Look for a vacuum leak in the intake. Idle the engine and spray starting fluid around gasket surfaces and any connection in the intake tract.

 

[ShawnQ]

Sprayed starting fluid all around the intake and no obvious change in idle, rpm, sound, or fuel trim readings. I don't think it has an intake leak.

I have not pulled the plugs yet, but will do that shortly.

 

[ShawnQ]

Also forgot to mention, no excessive fuel smell while driving or idling.
Fuel mileage seems pretty normal? High teens around the city, over 20mpg on the freeway (4x4 with stock 22" wheels/tires).
Power seems decent - although I've never driven another 6.2, so I'm not 100% sure what to expect. It's slower than I think it should be - but it's a big vehicle, so I may be overestimating it.

 

[jaxscuby]

pull the plugs on bank 2 to see if there are any differences in electrode color or condition
of the plug.

weirder things have happened..but it could be an out-going rear O2...but
again pull the plugs..

 

[ShawnQ]

Smoke tested the exhaust and intake - didn't see any leaks
I will pull the plugs this weekend. I was going to work on it yesterday, but on the way home the passenger rear window regulator decided to break and the window fell down (just before a storm hit) so I was stuck messing with that and replacing the regulator.

I'll let you know what the plugs look like