Ditto on that...the rough idling and possible misfiring would freak out the sensor, and cause it to spit out an error code.
Disconnecting the battery and waiting a few minutes before reconnecting will reboot the computer and reinitialize the diagnostics.
I think we need to start a forum on the OVP, as the posts in here weigh heavily in that aspect!
The OVP is a relay designed by Mercedes engineers to do one thing only...plague unsuspecting Mercedes owners with a whole host of problems that would stymie any logical troubleshooting process. Fortunately, the cat was let out of the bag early on, and we all know their secret.
Seriously, though, the OVP relay has been the source of a lot of peculiar problems, rough idle being the most common. The unit is small, easy to replace, but unusually expensive compared to a typical relay ($65).
Do a search on "OVP" and you will learn more about the care and feeding of your OVP.
2009 ML350 (84K) - Family vehicle
2001 CLK430 Cabriolet (71K) - Wife's car
2005 BMW 645CI (124K) - My daily driver
2012 Mustang V6 (60K) - Daughter's car