P0172 & P0175 2015 Suburban Ltz

[FarkM]

2015 Chevy Suburban LTZ 5.3 with 110,000 miles. At idle ONLY, I keep getting P0172 and P0175 codes. Not always, not everyday, but if I'm idling for a while the check engine light will come on and it's always those codes. DOD/AFM has been removed by a mechanic, the whole engine has been redone and they used a Diablo i3 to retune it. O2 sensors are brand new, PCV valve is brand new, MAF has been cleaned, air filter is clean. I am getting good readings from the fuel pressure, O2 sensors, MAF sensor, and fuel alcohol %, BUT my long tern fuel trims are at -35% when idling. What's left? HPFP? I know those were recalled in 2015, and mine was taken care of then.

 

[rdezs]

You'll probably get a better response in the 2015 to 2020 forum. You posted in the 2007 to 2014 forum. (Although production of your model actually started in January 2014 building 2015 models)

 

[jaxscuby]

The P0172 code indicates that the engine is running with a rich air-fuel mixture on Bank 1, meaning there is too much fuel or not enough air in the mixture.

The diagnostic trouble code P0175, also known as "System Too Rich (Bank 2)," indicates that the engine is running with too much fuel relative to air on the second bank of cylinders.

running rich on both banks of the motor. Take a good look around all the breather lines, vacuum lines, basically any hose that is around the intake manifold.
any kinks.

not enough air & too much fuel.

short term fuel trim is reasonable -4.7% & -5%.

-35% long term fuel sounds like the value is maxxed out.

during MAF scalar adjustments, revising the MAF table, grams/sec over voltage, depending on the values the AFRs for a given rpm
can be lean to rich.

Since you said you had the motor redone, it should not require a reflash of the ecu/rom file. But stranger things can happen.

but if you changes the way the motor breathes, the off shelf tune in the programmer might have the proper MAF table adjustments.

get ahold of your "Tuner" or call Diablo and explain your codes. they might have an update rom file for you.