One problem related to wiring has been reported for the 2003 BMW 330. The most recently reported issues are listed below.
Tail lights failed on my 2003 BMW 330xi. The shop foreman at my BMW dealership explained that he has been seeing a lot of tail light failures because the wiring was not designed to handle the load and therefore the wires have been frying out. My work order states repairs were done to diagnose & replace melted tail light connectors and wiring.