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My E55 battery has been draining to the point where letting it sit for 1 or 2 days completely kills the battery. To the point even the doors will not unlock .I had 2 new dealership batteries installed(front and rear) and had alternator tested (charging correctly) and no luck. I was told I had a alarm siren draining battery so I disconnected it and still didn’t solve the issue. Anyone know what the issue can be? I recently had my air suspension swapped with BC racing coils and the system coded to delete any suspension fault codes but I was told by the mechanic that this can’t be the reason for the issue.
I had a very similar issue on my 2003 E500 a couple of years ago and it ended up being a faulty power seat control module. My indie mechanic ended up diagnosing the issue, I tried on my own but couldn't figure it out.
Something is keeping the network of controllers from going to sleep. As mentioned, that can be a faulty controller or some type of electronic device added to the car that causes the network to stay awake. There have been many, many posts here on similar issues. Do a search. In a nut shell, you need to give the car sufficient time to go to sleep (10 - 15 minutes) and then test each fuse by pulling it to see if it is the one causing the high current draw. There may be more than one. Once you figure out which fuse is causing the high current flow you then need to figure out what is on that circuit and which specific device is causing the draw.
Mine was the audio gateway amplifier not shutting off. Drained the car in 2 days completely. The subwoofer would make a thumping noise every few minutes or so.
Don't throw money and parts at your car. Diagnosis it properly.
PM me your email address and I'll send you a large technical document that explains the CANBUS and how to diagnosis the problem.
You can literally determine the current draw on a circuit by measuring the voltage across the terminals on the fuses. You'll need to leave the trunk (or door) open but the switch locked down so the computer "thinks" the trunk (or door) is closed. Wait thirty minutes, then start measuring voltages. Once you find the circuit affected, start unplugging modules until the current draw stops. Voila, problem identified.
11-22-2022, 06:16 PM
