what is the reason for the check engine light on? on 2001 Jaguar S-Type

the check engine light just turned on today but the car feels great. what should i check?

Asked by for the 2001 Jaguar S-Type
The Check Engine Light indicates the vehicle's computer has detected a failure in one or more components of the emission control system. You will need to retrieve the codes stored in the computer to troubleshoot the problem. More info here;
1 more answer
Probably a CO2 Sensor!