OK David,
I took your advise and went to the www.odb2.com web site. The specific answer to the question: 'Will the ODB II, work on a 1994 C280', was not posted.

So, I sent an email to the sales department, asking if the ODB II would work on a 1994 C280.

There Response:
Hello Bill
Is your 1994 MB OBDII compliant?

Have you ever felt like you were in a Catch22 situtation?

Can anyone confirm there and/or my question?

Mr (Oh Nooooo) Bill