How do you turn off service engine light 1988 Volvo 740 gle?

Notice on the bottom right side of your speedo face panel a small round button

insert key until lights on but no start. take a dinner fork with out your wife noticing push the button firmly in. now open hood and disconnect the negative battery cable. Immediate reinstall cable. done. of course this loses all your radio pre sets so write them down first. That light comes on every 5,000 miles to remind you to change oil.