Why does the code not return, until after a few days, after being reset? on 2000 Chevrolet Tahoe

After inspecting the system and tightening the gas cap I reset the alarm via OBDII scanner. After a few days without any variable changes the alarm returns. My thought is that if there is an actual fault, then the alarm would return as soon as the vehicle is placed back into service. Why the multiple day delay? Codes P0440 & P0440Pd Chevy Tahoe 2000

by in Woodbridge, NJ on May 05, 2014
Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews
2 answers 1 comment
ANSWER by , May 05, 2014
Once you clear it then when it runs the EVAP test it sees the fault again to alert you of the fault. Fix the problem and maybe it will stay off.
ANSWER by , May 05, 2014
Use your scanner to run an EVAP test...then check live data to view componets....may need to run a movie while driving.. then check freeze frame data..
COMMENT by , May 05, 2014
Chitty Chitty Bang Bang? Hummm