Check Engine Light not working

The light should come on with the key as a bulb check.. The bulb itself may be burned out. You can only hope. Then depending on the brand and model, it should flash code 12 when the correct 2 pins are connected to each other. I can 't remember for sure which two on the GM cars. That was 30+ years ago. The Internet should tell.
One of my 96 Dakota's had the bulb in and working but the cavity was jammed full of strip caulk. Aparently the previous owner got tired of looking at the light.