When I had to get the smog done, I took it to the same shop that the previosu owner used to take. I dont trust him at all. Anyway, he spent 5-10 mins near the battery while the car was on and after that the light went away for 2-3 days. He told me it will come back on after few miles and it did. I checked the fuel filler cap, it seems to be fine.

Just to clarify, I have to turn on the engine before I go push down the button right?