Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hi, there is an antenna ring around the ignition switch that may have been disconnected or damaged when you removed the cluster. The ring reads the chip in the key to authorize starting. If the start is not authorized the car will start and die immediately. I'd take it apart again and check the antenna ring.
Let me know what you find.
It's typically going to be either a bad antenna ring or a bad key. Do you have another key that you can try?
It's not vital that you disconnect the battery when removing the cluster. You should at least inspect all of the fuses in the main fuse box and in the K40 relay located in the module box next to the battery. You should also scan the engine control module for fault codes.
I believe that you are saying that the starter will only turn the motor for 1-2 seconds. Have you tried jump starting the car? Low battery voltage can cause the starter to cut out prematurely. You can also try bypassing the starter relay to see if it will start.
Are you getting a "start error" message in the instrument cluster when you turn the key?