I have a 2010 Mazda 5 just bought used 30 days ago. check engine liht came on for a day then turned off? any possiblities?

Best to get the code or codes read, this will point you in the direction of a fix.

It could of been an evap code. Things like not tightening your gas cap will trigger this code if the system fails the pressure test. Once it's resolved, the light will go out by itself. It doesn't sound like a bad sensor, because the light would be on all of the time. Most likely there was a sensor that read a value that went out of range and then came back within it's normal operating parameters. If this starts happening more frequently or if the check engine light stays on, get the codes read with an OBD II Scanner to find out what sensor is throwing the code and then go from there.

most likely, it's due for a service- a lot of people will get rid of their cars without doing the required services- cheapskates- look at the mileage, see what the factory recommendations are, and find a good garage-

Thank you all very much really helpful.