Hello, been lurking for a while,need some help. I have a 2000 S500 with the cel light activated. I had the codes read and the codes po 170 and 173 came on. they cleared those and after driving about an hour, the same codes appeared. the next morning I started the car and no light. ahh the light did come back on after driving several hours. the car runs and starts perfectly. no issue that I can determine. can anyone tell me whats going on?where do I start. is it safe to drive w/o doing damage? thanks Bob