What do I do if the check engine light comes on
You will need to borrow, purchase or have a garage scan for the trouble codes with an OBDii code scanner. Any auto parts store can do this for free if you ask. The codes will tell you were to start looking for your problem. Not all codes for sensors means to replace them, it just mean that particular sensor is detecting a problem. You can give us the code after you pull them, and we can help further.
2003 mazda mpv minvan has ERROR CODE B0011 what does it mean