Aside from double-checking that you've tapped into the correct vehicle wiring (as follows) for your trailer harness, I would also double-check your ground connection. Make sure you are metal to metal (most surfaces are painted or coated in some way) with whatever connector you've used for your ground-wire to vehicle-chassis connection, or at least use a self-tapping screw that you are sure is tapping into some part of the VX's metal frame. There are also a lot of rubber grommets used on various pieces of the VX that isolate that part electrically from the chassis, so sometimes even though it may seem that a good ground connection is being made, that's not necessarily the case. A simple test meter check will let you know for sure.
RT Turn Signal Wire Color (only avail on the Passenger Side): Green/Blue
LF Turn Signal Wire Color (only avail on Driver's Side): Green/Blue
Parking/Running Light Wire Color: Green/Red
Brake Light Wire Color: Green