If your brake lights won't work niether will your traction control.
Vehicle Application: 2003 Cadillac CTS 3.2L
Customer Concern: Left and right brake lights inoperative. Shift interlock intermittently inoperative as well. Tests/Procedures: 1. Check battery voltage at stop lamp switch Red/White wire terminal "A". If no voltage, check STOP LP SW fuse.
2. Check for battery voltage at stop lamp switch White wire terminal "B" with brake pedal applied. If no voltage, replace stop lamp switch.
3. Check circuit 17 (White wire) integrity from stop lamp switch to stop lamp bulbs. This circuit goes through two splice packs, SP200 and SP302.
4. Check stop lamp bulb ground circuits for opens/high resistance.
5. If circuits are OK, check for faulty stop lamp bulbs or sockets. Potential Causes: Bulbs Sockets Stoplamp Switch Wiring
Tech Tips: SP200 is under the instrument panel, above the steering column. SP203 is in the passenger compartment, on the frame rail, left of the driver's seat.
My car did this recently. My brake lights (passenger and drivers side as well as 3rd light) were light up constantly and burned out. Replaced bulb- still on constantly. The EBCM went bad and the brake panel lights on dash were illuminated. Replaced EBCM at dealership.