congrats on your purchase! My girlfriend also has a 2007 x3 3.0si. She purchased it having ~39,000 miles. Now at 88,000 miles the SEL came on. I had the code run through the local autozone and it returned "P0597 | Thermostat heater control circuit open". Probable cause "Failed engine cooling thermostat". Its weird because the car gave no indication of overheating and continued to run just fine.