Had my helper check the brake lights, and to my surprise they were all working - yet same message on the console. Checked the bed cargo lights, which were working, and it dawned on me that the third brake light should be coming on, and it was out. How refreshing that only a phillips screwdriver is required to pull out the third brake light. Found the bulb had actually blown apart - never saw that before

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Of course those bulbs are different in the third brake light than the actual left and right brake lights - so back to the auto store to pick up a Sylvania 921 pair of bulbs! Problem cheaply solved...