2001 S40 Brake Lights are not working. Middle brake light does work when I take the bulbs out of their socket. Have taken to two mechanics. Best thought is the Bulb Integrity Sensor. Does anyone know where it is located? When the bulbs are in their socket but not working, no warning light shows on the dash, but when the bulbs are out of the socket the warning light appears. I have tried another CEM, but that was not the issue. Brake switch is working because middle brake light is operational. Any thoughts or solutions would be appreciated. I am using the rear fog light as a second brake light, but it is not very safe to keep turning on and off the switch when hitting the brake.