Let me answer my own question for the record. The CCM must be able to sense a resistance change when the bulb is getting weaker and throws an error message, kind of like an early warning. Replaced both brake light bulbs - #921, $4.99 for two at Pep Boys. 5 minute job each side:
Peel back the interior carpeting to access the back of the tail light.
Disconnect the electrical connector.
Unscrew the spring'ed fastener to release the tail light from the back of the car.
The tail light will then easily slide off the back of the car.
Unclip the plastic piece (5 or 6 clips, be careful not to break them) and remove the bulb assembly from the tail light.
Replace bulb using gloves so you don't touch the lamp itself.
Plug in to the electrical connector to test to make sure the new bulb works.
Installation is the reverse of removal.
