brake warning light on B2200

Occassionaly the emergency brake warning light comes on my dash, but there are no problems with my brakes (that I can make out). Any suggestions?

Rear brakes (inc. emergency brake) are anti-locks.Sensor on antilock sometimes goes bad and reads out on dash as emer. brake problem.Have it checked plus check ti be sure emer. brake is releasing completely. B

Also make sure there is sufficient brake fluid in the reservoir, as there is a float which will cause the brake light to come on if the fluid level drops too low. And these trucks are known to have leak issues with brake and clutch cylinders; I know, I've gone through a bunch, but lifetime warranty...my 1988 B2200 does not have anti-lock brakes.