My 2002 325i (E46) service-engine-soon light came on and next to it, "EML". I have 105,000 miles on the car. Do I need to purchase a diagnostic scan tool to read the codes and reset the lights?? I believe they cost on the order of $150. Seems like a good investment, but I'm looking for advice. I do all my own maintenance, but have not had any lights come on before.