I own a 2000 SLS with 100,000 miles, and yesterday I was sitting at a drive through window and the car stalled. I restarted it, and the "Service Engine Soon" light came on and stayed on during my 20 mile drive home, but the car drove normally. When I got home I read up on how to enter diagnostic mode, and the displayscrolled quicklythrough every code option, some saying no codes, and a few saying code #### (didn't write them down) history. The display then went to "Clear all codes?", at which point I switched the ignition off, figuring that the code histories would be saved. I took it into a service shop this morning for an engine diagnostic, and I noticed the "Service Engine Soon" light was no longer illuminated. The service shop just called me to tell me that they couldn't find any codes. I havetwo questions:
1. Could I have cleared the code histories and "Service Engine Soon" lightby turning the ignition off in diagnostic mode?
2. Will the codes come back if it is a reoccurring problem?

At this point I'm just having the shop perform the recommended 100,000 mile maintenance, but I'm worried that something is wrong. Any help is greatly appreciated!

 

If failure is still present, codes will reset