Ok , I just want to start off by saying thanks to you if your even reading this lol. But here the story goes. So I bought a 2003 e320 with a few cosmetic problems. Put new battery and the car was running fine. But would drain battery if I let it sit for 3-4 days or so. One day at work, people are calling me and telling me that the alarms keeps going off and the trunk lid keeps popping by itself. So I asked a guy to toss something on the trunk tillI made it back to the warehouse to punch out. When I got back. Battery was drained and so on. I put jumper cables on it and let it charge for 10-15 min. Car finally opened up and started. Now on the way home the car dash starts red light flashing saying low battery low battery brake failure. So of course. I slow down turn car off and restart, and it was fine. Half way home on highway same thing starts again. But this time I keep driving and after about 5 minutes. The car goes into limp mode I think. It would go past 50mph and the radio shut down and the interior lights shut down. Crazyyy. So after 5 min the car came out of limp mode while on highway and ran fine. I get home turn car off wait 5 min and the car starts fine. So I'm like something's going on. So I drive my truck instead. Weekend come around and I get started on trying to see what's going on. I did research and seen that it might be the trunk harness. I get into that and find four wires totally frayed and bad. So I fix them and get them together. So at this time the batteries dead because it's been sitting for 3 days. I try and jump no luck. I get another battery and no luck. So now the cars just dead. I hook at battery pack up to it and the trunk lights come on and the single dash circle comes on and head will come on if I turn the knob. But key fob won't lock or unlock doors and the ignition won't accept the damn key to turn the ignition! I thought maybe the Sams unit. But I dunno,,,,,, Thanks a lot for any help guys!! MBSTRONG 👊🏼👊🏼👊🏼👊🏼

 

Sounds like all those shorts and battery jumps could fry your computers.
Get reliable battery, put it on and give it a try. Check the small battery and if it is dead- disconnect it for time being. If that doesn't help - you need SD to troubleshoot.
Good luck.

 

No one with any answer??

 

Look, your car has approximately 32 digital modules controlling various sub-systems of the car and they all communicate with the CGW over a 2-wire bus. Rule one with these cars: NEVER have the key fob in the ignition when disconnecting a battery, reconnecting a battery, or attaching jumper cables. With the key fob in the ignition, the circuits are energized and voltage spikes can fry electronics. Big problems. FWIW, I know one guy that found a total of five fuses blown after connecting jumper cables to his car with the key fob in the ignition. Will it happen every time? Probably not but Mercedes tech docs state explicitly to not have the key fob in the ignition in the instances mentioned above.

Somewhere you have a bad module that is draining your battery. To find that module, you need to connect to DAS (best case and *strongly* suggested) or an aftermarket code reader that handles MB codes. The catch is you have to be able to turn on the ignition switch to position 2 and yours won't turn.

Now you're going to have to check virtually every fuse in the car in the hope it is just a blown fuse and not a fried EIS.

Start under the hood with the front SAM paying particular attention to f43, f44, f57, (ECU power depending upon engine), f80 goes to the steering column; the other fuses control other modules. I can't tell you more without firing up the computer and inspecting schematics and I don't have time to do that.

Won't hurt to check the fuse box on the driver's side dash. Then check the fuses in the rear SAM in the trunk. If you still haven't found the bad fuse(s), inspect the pre-fuse block in the trunk next to the battery and then pull the passenger side floorboard and inspect the pre-fuses under the floor. If you can get the ignition switch to work again, stop screwing around and put it on a proper diagnostic system.

Tip, you can either pull and visually examine each fuse or get a multi-meter with good probe tips (small and sharp), set it to lowest resistance range (should give you an audible tone with a good fuse) and just touch the probes to either side of the fuse top where you can see the metal leads.

 

Here are the locations of the fuse blocks.

 

 

Can't remove the prefuse under passenger foot for inspection. I removed the two nuts, is there anything I'm missing to remove it?

 

I've never taken one apart so can't help you there. PM me your email address and I'll send you some troubleshooting information.

 

So I've checked all fuses and also opened up both pre fuse blocks and nothing is blow. I think the only thing that was blown was the number 9 fuse on rear same which is the rear defrost. Now I'm stuck ((

 

Stillll no luck .

 

I let my e500 battery die the other day and a jumper box couldnt jump it. jumper cables on a running truck. Still nothing. I had to use a actual battery charger. I had to charge on 25amp for about 2 hours then. Did a repair through the charger. Just a function on most chargers for completely dead batterys. then charged on 10amp over night. Then it finally had enough to get going. It takes alot to power all the electronics and the airmatic first initial rise on start up. You can get a charger for around 50 dollars US. Might work might not. Thought i blew a fuse to. But this seemed to work for me. Good luck!

 

 

Sounds like more than one problem consider checking siren unit (f8 @ rear SAM - trunk) next, internal board may be malfunctioning as described due to corrosion. See capture to shop used compatible part #s, and attachments for replacement.