P0171 Lean Condition w/ Troubleshooting Steps Taken/Data Logs

[Eric McArdle]

Hi,

I'm having an issue with my:

2016 Chevy Silverado 5.3L V8, 76.5k miles
P0171

Symptoms: Truck runs fine mostly but has about a 10% reduction in fuel economy. After running for a while and idling, randomly, the truck will experience a rough idle during which short term fuel trims will spike. The truck starts fine and from what I can tell, has no loss of power while running. Given that rough idle/code takes some time to occur and can often be "reset" by clearing codes, it makes me believe I have a valve or something mechanical that is malfunctioning to create a lean condition.

In the last 2k miles, I have replaced:

1. Spark plugs and coil packs
2. Oil and filter change
3. Air filter check (clean)
4. Mass airflow sensor
5. Mass Air Pressure sensor
6. Ambient air temp sensor
7. EVAP purge solenoid
8. PCV Valve
9. Transmission replaced (stock failed)
   1. At this time, I also had rear diff and transfer case fluid changed

 

I have smoke tested my air intake and don't see any leaks. I also smoke tested the exhaust system (above) with nothing noticeable. Attaching freeze frame and data log.

Any ideas? Thank you.

1GCVKREC9GZ198543-RepairReport-2023-07-30-04-01-24.pdf Data log.pdf 1GCVKREC9GZ198543-freezeframe-2023-07-30-03-59-6.pdf

[rlcole321]

Looks like you might have a bad injector(s) (or a restricted fuel rail) on bank one, if you can get the use of an inferred Laser temp reader, when the eng. is cold, remove the heat shields from the manifolds, bring the the eng to temp, shoot the runners for each cylinder get a reference, then have someone "Power-Brake" it in gear and take another reading(on both sides). You might find lean cyl.(s) which will be a colder reading.  The you can go from there.

[silveradosid]

freeze frame show the code tripped at 1200 rpm's, you are going to need a better scanner to find this problem. it could be a slow responding o2 sensor or a weak injector. need to do a cylinder balance test and be able to graph it see what bank one is doing just before it throws the code and after

[Nikki3721]

Did you figure out the issue? I have the same code and symptoms in my ‘15 Sierra. Just purchased cats and o2 sensors to change out once weather clears, just really hoping it’s related to those. I did not previously have any codes, but a bad rattle and exhaust fumes coming in the cab.