jdwilson112

2004 c230k...intermittent problem when starting my car. The key will not turn in the ignition and it seems to be putting the car in some sort of safe mode, it cuts all power to the car, door locks, interior lights, etc completely dead. I either have to wait for a while and it will reset itself so I can try again or I have to disconnect my battery and manually reset the system. Usually it will start after I reset. The problem first happened when my primary key died in the ignition, I have since replaced the battery in it and this problem occurs now with either key. Both keys have new batteries and the red light is bright when I push the button, car has a new battery and is charging fine. I'm thinking possible ignition switch or a relay, any advice on how I should diag this? The ignition switch was already replaced about 15k ago by previous owner so I hope that didn't go bad again.

jdwilson112

Update on the starting problem, I found another key in my garage that I know is from a different MB and tried to use it in my ignition, of course the car didn't start but it also did not go into a "security" mode and cut power so I don't think it has anything to do with not reading my key correctly. What I did notice when I paid close attention is that when I stick the correct key in the ignition it will make a noise that must mean it recognizes the key and pairs it with the vehicle (kind of sounds like the ignition is electronically grabbing the key) It makes the same sound when I pull the key out of the ignition.


I assume there is some sort of module in there that tells the car when the key has been paired to it and this might be the source of the problem. I suspect that the times my car doesn't start are when I pull the key out of the ignition and the module isn't resetting so the next time I put the key in it gives a fault and shuts everything down. Now that I know what to listen for I am going to pay close attention when I turn the car off and on to see if my theory is correct.


Now if anyone knows what this module is called or how to bench test it please let me know, I would rather rule this out before it happens again so I don't get stuck somewhere away from home.

Holmes5518

The module you speak of is your ignition switch.

Glyn M Ruck

https://mbworld.org/forums/c-class-w...t-process.html

jdwilson112

Thanks! This is exactly what I was looking for. These cars are a lot more complex than my Fords. I'll start going through the system this week I'm sure the issue lies in there somewhere.

jdwilson112

Ok I started going through the system, fuses and relays are good. I was doing some more research on the issue and I'm now leaning toward a faulty EIS. I read that trying to start the car with a weak battery in the key can cause memory loss to the EIS which may be irreparable . Well this problem started when my key died in the ignition, makes sense to me.


So is there a way to test the EIS without taking it to the dealer? Also can I replace the EIS myself or do I have to get it programmed at the dealer? I'm trying to avoid taking it in because I know it's going to be expensive.

samaritrey

From my understanding the EIS has to be installed and programed by the dealer as they won't sell you the part.

tommy

Yep, you can now enjoy the dealership experience.

Expect 1500-2200. But the free donuts are priceless!