NHTSA Complaint #11644047 — 2018 GMC TERRAIN

My check engine light comes on intermittently, since March 2024, after having Cabin & Engine air filters replaced. Each time, I’m told it is code P0171. This has happened too many times for my comfort. Usually, it happens around the time my gas gets below 1/2 tank or after I fill up my gas tank. Originally, I was told by the mechanic that it could be one of four things, of which I’ve now had some of things done. InIn Aug. 2024, the check engine light came in. Code was P0171. Mechanic replaced the Brake vacuum pump. Once incident, almost a month later, on 9/24/24, was very scary. While driving on the interstate, I got ready to increase my speed, but heard a pop sound and noticed the speed wouldn’t accelerate. Next, the check engine light came on and the message in the dash popped up saying “engine power reduced” or something similar. I was able to coast from the fast lane over to the slower lane and off the highway into a parking lot. I turned the truck off. When I crunk it back up an hour later, it was shaking and jerking. While slowly driving, on the way to the mechanic shop, it jerked and shook each time I tried to accelerate after stopping at a light or slowing down with traffic. The code again was P0171. According to the mechanic, the intake hose had popped off. On 11/13/24, the check engine light came on. I again took it to have the code scanned and truck looked at. Test results again showed P0171. This time the Mass Air Flow Sensor was suggested. In a year I’ve had the fuel system cleaned twice, brake system flushed, & other routine maintenance such as oil change & brakes. Yet, my check engine light seems to still come on intermittently atleast once monthly. It came on two days ago, 2/18/25, when my gas was around 1/4 tank full. I added a fuel system injector, per mechanic suggestion, and filled my tank up with gas on today, 2/20/25. The check engine light had gone off within about 15 mins of me driving. I’m certain it will be back on soon with the same code.