For test purposes the OVP acts like a fuse and tests like one. Power in and power out. thats all it does. Since it is rather hard to test at the ends of this fuse, it is usually easier to see if the devices powered are powered. ABS as Doc pointed out tells one part of the circuit. The KE controller is another. The easiest way to tell if it is powered is to evaluate EHA current or duty cycle codes. Look at the DIY article for evaluating engine controls to see how to do this.
All the answers to OVP can be seen with either ABS, EHA, or idle speed current. Although the most common faults knock out all of the above. I have seen every circuit fail separately and differently (more than one type of symptom).
Bosch Master, ASE Master, L1
33 years MB technician