The check engine light (service engine soon) comes on and stays on when a problem is detected by the self diagnosis system of your vehicle. Generally, the problem is in the emissions or something that is affecting the effectiveness of the emissions, but other causes can trigger the light to come on, too. To determine the cause, the vehicle will need to be taken to AutoZone or a shop that has an OBD2 scanner, or for 1995 and earlier models, an OBD1 scanner, While a scanner will not give you the magic answer, it will give you a code that narrows down the problem area.
Check your fluid levels.
Fix the problem causing them to be on.
To reset the check engine light unplug the battery for 30 minutes. If the issues still persists the light will still light up when reattached.
There is an engine misfire, probably spark plugs issue.
this is for safety so engine does not get ruined,check oil level!!
Get the computer scanned to see what the problem is.
There are pages and pages of things that can cause a check engine light. You need to have it checked with a scantool. Then the code can be diagnosed and repaired.
Disconnect the negative battery terminal for at least 30 seconds.
Any failure that can increase tailpipe emissions.
If the check engine light is illuminated, start with scanning for codes.
The most likely cause o f the check engine light is that the belt was not tightened properly. It may also be that the belt stretched and needs to be retightened.
I am not sure of the other 4 reasons But in my experience the top reason your check engine light comes on is because your gas cap isn't tightened all the way.