95 / 96 MB cars did have an OBD 2 testing issue , I've read state emission testing manuals that call out these cars as being trouble. 95 / 96 had a translation box on top of the regular engine computer that generated OBD 2 info. However this issue is unrelated to your 2000 car.

97 and up has Bosch ME ( motor electronics ) where OBD 2 was built in so it should be OK to read. Others on this list have similar cars in CA and this is the first in memory that a problem like this was posted.