There are a few possibilities as to why the trailer brake lights are not working. First, you will need to make sure that you have the wiring from the harness connected to the proper wires on the 2003 Saab 9-3. The # C59496 harness can be wired in different ways depending on how the vehicle tail lights are wired.
To determine if the vehicle is the problem:
You will need to determine if the vehicle has a 2 wire or 3 wire system. A 2 wire system will have the same bulb for stop and turn signals.... view full answer...
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