Let’s close this. The issue has been resolved. A new battery did not correct the problem. The CEL did come on. The code was P0123. A new throttle pedal was ordered and installed. Since the installation of the new pedal there have been no throttle related problems.

The pedal is Mercedes, for a 2003 SLK 320. Part number 170-300-02-04.

Again, thanks for the assist.