as per the mechanic,there may be some problem with the gas tank cap and just reset the engine and replaced with a new cap,but problem came up again after a while and on/off after refilled few times,is there a electrical problem with the sensor or should be something else ?so far not seeing any specialissue on temperature or gaz milage.

its probably your oxygen senser advanced or autozone can tell you only when lite is on

You have to make sure the cap is tight every time you refuel. There maybe some one else opening your gas tank so check it before starting.
BTW-
l would like to have a nickle for every one that replaces an O2 sensor because the check engine light comes on. More then likely it needs a tune up more then the O2 sensor replaced.