Check Engine Light On problems of the 2010 Dodge Caliber

While pulling into traffic from a parking lot, the car would not accelerate, despite my best attempts, finally after several seconds of coasting and the pedal pushed all the way down, the vehicle jumped into acceleration. During this incident, the check engine light came on. I promptly took it to the dealer, who ran the code and it said p0455 large evac leak. The dealer ran the esim test and vac test with no results. They told me that I probably had a loose gas cap. I had not been at the gas station in days. Also, when the gas cap is loose, an error abbreviation for gas cap shows up in the mileage readout and does not come back on after the cap is tightened. I have never had the incident described above occur because of a loose gas cap. No further work or diagnosis was done on the vehicle.