How do you reset the Engine System Service Required light in 2004 Volvo XC 90?

To reset the Engine System Service Required light in a 2004 Volvo XC90, first turn the ignition on without starting the engine. Press the gas pedal three times within five seconds. After doing this, turn the ignition off and then start the vehicle; the light should be reset. If the light remains on, it may indicate an underlying issue that needs to be addressed.