One problem related to wiring has been reported for the 2003 BMW 530. The most recently reported issues are listed below.
The car caught on fire on 9/4/18, and caused extensive damage inside the engine bay. Car was driven several miles to a store. The passengers were exiting the car when they smelled something burning. Then they noticed smoke and flames extending from the front of the car. The fire started in the passenger side and was extinguished before the drivers side also caught on fire. The insulation on passenger side wiring harness is completely burnt, and numerous other items including the fiberglass body. The vehicle had approximately 215000 miles on it, and was well maintained. No recent repairs had been made to the engine. No smells of gasoline, oil, or plastic burning were evident before the moment the fire started. The cause of the fire is unknown to us at this time.