I have a 99 E300 TD. A.T. 168,000 miles. The SRS light flickered a little bit while driving & has stayed on since....all the time....doesn't matter whether a passenger is seated or not. Everything else works fine. No recent work done. I pulled the codes on the Air Bag system and none are present (no current codes, no stored codes). Any advise on where to start looking? How to check? Thanks! -Tim