Answer
Most of the time when the emissions light is on then there is a diagnostic trouble code stored in the computer, you will need to get a scan tool to read the code and clear it, but it depends on what year your volvo is. also it could be a normal maintenance reminder to replace the oxygen sensor. you will need to post another question with the specific year model and engine your vehicle has. or you can email me and i will give you more info if you pick me for best answer.