What should I do when I see the check engine light on in my car?
user
If the light is on and the car seems to be running normally, then just make a note to yourself to have a mechanic take a look.  You don’t need to take it to the shop just because you see the light.
assistant
So it's usually not anything major?
user
Usually.   If you see the light on, but the car feels like it is misfiring, you should probably take it to the mechanic to see if something serious is wrong.
assistant
What are the common reasons for the light to be on?
user
The light could be on if something isn’t attached correctly in the car.  Or it could be on if a sensor in the car is broken.   It could also be on if there is debris in the exhaust system.  Or it could be on because of a bad sensor, bad wiring, bad gas, or because of the spark plugs.
assistant
Can I reset the light on my own?
user
The light can be reset by disconnecting the battery for 5 minutes, and then reconnecting it again.  You should avoid this if the light is on because of the spark plugs.
assistant
What should I do when I see the check engine light on in my car?
user
If the light is on and the car seems to be running normally, then just make a note to yourself to have a mechanic take a look.  You don’t need to take it to the shop just because you see the light.
assistant
So it's usually not anything major?
user
Usually.   If you see the light on, but the car feels like it is misfiring, you should probably take it to the mechanic to see if something serious is wrong.
assistant
What are the common reasons for the light to be on?
user
The light could be on if something isn’t attached correctly in the car.  Or it could be on if a sensor in the car is broken.   It could also be on if there is debris in the exhaust system.  Or it could be on because of a bad sensor, bad wiring, bad gas, or because of the spark plugs.
assistant
Can I reset the light on my own?
user
The light isn’t always a big deal, so if you have a reliable car you could just check the car’s manual to see how to reset the check engine light. 
Otherwise, just take the car to a mechanic if you are having trouble with it.
assistant
What should I do when I see the check engine light on in my car?