I know this thread is old, but i had the same situation with my 2012 LS 2.4 had the p0171.
its a lean problem. I found that it was a un monitored air problem. caused from either a vacuum leak or dirty MAF. I found that the service station that serviced the car before I bought it. forgot to tighten the hose clamp that leads into the throttle body and they did not replace the air filter housing securely.

An update to the Dec. 10, 2020 post about the 2015 Malibu P0171 error -- The dealership had it for a day and a half and finally diagnosed the car as having 3 out of 4 sticking fuel injectors which cause the long term fuel trim to run high (lean fuel mixture) and so the check engine light comes on sometimes. The engine performance is good outside of the lean fuel mixture issue. I was told it probably wouldn't be worthwhile to replace the injectors since the performance of the engine is pretty good as it is and would run indefinitely as it is anyway. The check engine light goes out many times when using a gas would a good cleaner like 87 octane Shell gas.

yes false air....air not measured by the maf sensor will cause this. This is why i asked the op to note the rpm the dtc set at. vacuum leaks create a lean mix at idle but fuel trim returns to normal at higher rpm.
to terry 500 if there is no updated programming; its not a glitch. running lean isn't a good idea. lean burn/slow burn creates higher combustion temps.

More P0171
 

So in my 2015 with the same engine I have had this code before and they replaced o2 sensor. Now what is strange is the light goes out at 1/2 tank and comes back on if I fill it up. Thoughts anyone?