The bulb integrity sensor found on the 200, 700, and 900 models has been known to be prone to failure, namely on the brake light circuit. The two most common failures are no brake lighting at all, or a failed bulb indicator lamp that won’t go out. Before considering integrity sensor replacement be sure to cover the basics in this system first. 1. Fuse, 2. Brake switch, 3. Taillight circuit boards, especially at the connector. & 4. Bulb and socket condition. Since the integrity sensor measures the difference in current draw from side to side the bulbs must also be the same brand and wattage. After eliminating these other possibilities the integrity sensor is a likely candidate for replacement. To diagnose the sensor itself, follow the wiring diagram in your service manual with a test light and look for power into and out of the sensor.
Note- Early 200/700 series came with a BLACK integrity sensor, our YELLOW sensor replaces the early black ones. Later model Volvo's had RED sensors, be sure to double check the color of your sensor, especially during the crossover years.
