Two problems related to tail light switch have been reported for the 2013 BMW X3. The most recently reported issues are listed below.
There is a faulty chip in the tail light. This causes a failure of the tail light with no advanced warning. Typically when a bulb goes out the driver will get a warning in the gauge cluster. This faulty chip prevents the warning.
Tail lights will fail with no warning light or message displayed in dash board. X3's equipped with hid headlamps come with four led tail lamps. In each lamp, there is a circuit board that will fail due to poor quality control (the resistors and/or capacitors will get detached from circuit board) , therefore, the lamps will stop working. Usually, when lights burn out, the dash warns the driver, but not for this failure. The owner could be driving at night with no tail lamps, and it could lead to a rear end collision.