1993 190E No CEL, but bulb good
 

I am having a hard time figuring out what is up with this car. It needs the emissions test, but the Check Engine Light does not come on. The bulb is good, in fact, I pressed the black button on the little panel in the engine bay (rectangular plastic piece with a cover, and approx 6 holes in it numbered. The button is just above the 2. When this button is pressed, the CEL illuminates, so I know the bulb is good. Anyone know what to check?