Why does the overdrive light keep blinking on a 1996 Mazda 2300?

A flashing OD light means there is a problem with your transmission. Your truck should continue to operate, but without overdrive capability, have it checked out at a shop. Your Mazda Pickup is almost identical to the Ford Ranger and thus should have a Ford transmission, when there is a problem with the transmission the OD light with either come on or Flash and sometimes the Check Engine light with come on too depending on what is wrong with the tranny.