Ross,
The OVR {Over voltage relay} is kind of a voltage spike protection supressor. It may be different on your model than mine, [ E320], but a search on OVR will get you the info that helped me with mine.
I got a new one from Parts Shop and the new was an up-dated part # as the original was troublesome. { As the Search will indicate ]
Aside from the ASR light,the new one also solved some stall and start problems
also common to OVR's .
Check with Parts Shop and see if yours has been updated.
Arthur