Very hard to say what it could cost as it all depends on what the actual cause is. A bad ground at the light would take less to repair than if it is a broken wire halfway up front.
This vehicle further complicates that as there are two different control systems depending on what time it was built.
One item you can check before you go there. If this is an early build car (before May of 2005) there may be a simple solution. Check the fuse panel on the left side of the dash. You are looking for fuse number 4, it is a 5 amp fuse and it powers the license plate lights.
Wednesday, August 30th, 2017 AT 8:02 PM