Service Engine Soon light on 1992 Chevrolet Blazer

When my truck idles for a few minutes, the Service Engine Soon light comes on and will not go off until I shut off the truck. What would cause this?

Asked by for the 1992 Chevrolet Blazer
1 answer
This is the Check Engine Light, and there is background on what why it comes on and how it behaves here: http://repairpal.com/check-engine-light