How do you turn off the 'maintenance required' message on the dash message cneter on the 2007 Volvo S40?

Answer 1

Put the ignition key into position I, push in and hold the odometer reset button (use your left hand), move the ignition key to position II, when the service light begins to blink,let go of the odometer reset button. Confirm by turning your Volvo off then on again.

The previous description was for resetting the "Service" light.

To reset the check engine light, the car must be plugged into either an OBDII compliant scan tool, or a dealer's scan tool to retrive whatever trouble code has been stored, repair the problem, and then the light can be "reset".