Yes the central locking system still works with keys in the door, trunk or the switch inside. Its the inferred or coding that is not working. Both the remotes have new batteries and the test lights work on them.
Sorry Peter I dropped the ball. I was looking for some simple tests you could do to diagnose the system but most everything requires the Mercedes hand held tester. Have you checked fuse #17 and #14 in the main fuse box? Have you tried to synchronize the remotes?
I will check fuse #17 and 14 in the main fuse box. Is that located under the rear seat or engine compartment. Also are there special steps to synchronize the remotes other than put the key in the ignition or door lock and turn and hold a couple of times?
The fuses will be under the hood in the main fuse box next to the brake booster. Do you have the folding switchblade type key or do you have the infrared key pictured below?
I have the folding type key with the blade and the single center button in the middle