1st thing to check is the connections to the locking mechanism. since the fob and inside switch fail to operate the locking mechanism, the fob and inside switch are good. Perhaps the receiver or lock itself is bad. Have it tested before replacement.
What should i be testing.
Diamond, The inside locking mechanism of course, suggested by John. I do not know if there is any computer glitch. I would do whichever is most convenient and least expensive first.
Looking for a Used CLK-Class in your area?
CarGurus has 1,548 nationwide CLK-Class listings starting at $2,499.
Search Mercedes-Benz CLK-Class Questions
Mercedes-Benz CLK-Class Experts