hello welcome to the site
we have been seen a few hid control units failing.
their is not any real test for these other then swapping the left and right control unit.
if you check power to the 2 pin connector and you have power then its a bad control unit.
the front bumper will need to be removed and the head light unit will need.
you can use a ohm meter to see if the unit is failed or a wiring problem.
you might be able to see and unplug the connector with out removing the bumper.
if their is moisture in the head light you will need to replace the head light assy and the hid control unit.
these control units short out very easy to moisture.
the bumper will need to be removed to replace the control unit and the head light assy.as long as the connector is unplugged your ok.
the control unit screws on the under side of the head light bucket.