John5788

Hello,

I have a 2003 E320 that has developed a severe battery drain issue. I've connected my multimeter in series with the positive terminal of the battery and measured 1.98A of current while the car has been idle/sleep for about 15 minutes. Driver door has been "locked" and left physically open with the alarm armed so I can measure the voltage drop across fuses in the engine bay, left of dashboard, and trunk areas.

I recorded all of my measurements of detectable voltage drops across all of the fuses and have compiled them into a spreadsheet for easier viewing:



I'm hoping someone with some deeper knowledge of this car/platform can help me figure out what's going on. I believe the current draw detected across these fuses are just symptoms of one or maybe two failure points with the electronics of the car.

If anything seems weird, I can remeasure or double check my handwritten notes.

Any ideas?

John5788

I poked around some more and found the culprit, Fuse 34, driver seat module.

I started pulling the high current draw fuses with no good outcome. For example, pulling both F84 and F85 reduced the overall current draw down to 1.5A, which is what you would expect. But going down this path of troubleshooting/fixing would mean I would just have to pull all the listed fuses above with detectable current to resolve the battery drain, which isn't the correct answer.

Following my original hypothesis, I reinstalled the fuses and went back to pulling single fuses with the same outcome until I hit F34. I removed F34 and let the car sit idle for 5 minutes to let the electronics sleep and discovered the battery drain reduced to 60mA. So something driver seat control module is causing all of the other electronics to wake up and chatter across the network for an accumulated total of 1.98A draw at idle.




Thanks for the help, it looks like I am in the market for a new driver seat control module.