Thank you. I just got truck last week. Most of the stuff is maintenance. Exhaust manifold was cracked when I got it. Had it replaced by shop. Only did a maf as a result of this code. I just tightened all the manifold bolts I could see through the wheel well.

I didnt have this code until I filled up and ran a half tank with Lucas deep clean fuel treatment. (Like seafoam)
I see shop put my old upstream o2 sensor in new manifold.


Things i have done.
Check all connections
new breather hose
spark plugs
tighten manifold bolts

not able to check fuel pressure at this time. When I button it back up I will see if manifild bolts tighten did anything. All I could get to needed a few turns but weren’t loose.
maf sensor

 

What fuel did you use? Notice any performance issue after fueling?
Fueling with a fuel where the concentration of ethanol exceeds maximum % recommended can cause P0171.

 

check the intake manifold bolts as well for air leaks and vacuum lines.

 

Just went for test drive after tightening intake bolts. No change. Truck runs really well.

I live in NW indiana Chicagoland. We have ethanol in our gas. I got gas today at Citgo. Last week when I bought it the tank was low on fuel and I filled it up at BP Amoco and added the Lucas Deep Clean before I filled up and tank was nearly empty.

You know what.. this is the time of year we usually switch to summer blend gas. You might be onto something with that.

 

Pure-Gas

 

This guy had same problem in Trailblazer and changed air solenoid....great video

 

Shop found intake manifold gasket minor leak. They are replacing intake gasket.

 

Never run on low gas in the tank because Ethanol attracts water, which is heaver then gas so the water builds up at the bottom of the tank
and running on low tank will then suck up mostly water.
Use a product that dries up that water
Maybe best is to flush gas tank and be SURE when filling gas tank not pumping in E15 gas which most people do not know has existed for 4 years
and people are NOT looking at the pumps or asking if that pump has E15

Your not reporting what size the engine is, the DTC, is reporting LEAN on left head, what are the LTFTs reporting on right head ?
If the other head the LTFTs values are closer to zero then put all effort to the head that is the leanest
but +23% lean reported is max lean
Bad gas, wiring problems, like to O2 sensors, air or exhaust leak for that head
check ign coils for that head
Dirty weak or bad fuel injectors

 

Also check for smog pump
Off each exhaust manifold is a hose from the smog pump,
there is a check valve that allow the air from pump to go out exhaust but NOT into the engine
IF that check valve is stuck open then air would be injected into that side of engine and cause huge lean conditions

 

Thanks..It is the 3.7 I5. The shop is doing intake manifold tomorrow. Said it has a vacuum leak. I have read about smog pump. It has a brand new exhaust manifold, bolts, cat convertor and O2 sensors.