Date registered: Jun 2007
Vehicle: 2003 SL500 and 2003 CL500
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Could the source of my battery drain be the drive-by-wire system?
Last year my 2003 SL500 started having the rear trunk accessory battery go flat. The battery was replaced, and the new one was doing the same thing shortly thereafter, draining the battery within a day or two. I took it into the shop, and they told me there was definitely an electrical drain coming from somewhere in the car, one of the computer modules was apparently not shutting off.
After 12 hours of them disconnecting modules, unhooking this and that, they couldn't find what was drawing the current. But now I have an idea...
I heard my car in the garage one day make a noise that sounded like a generator, or a pump...making almost a grinding noise that lasted for about 3 seconds. I have heard this same noise previously at times when unlocking my car, but have noticed it also do it when I get in the car and my foot touches the brake pedal to prepare to start the car. My car makes this noise about once every hour now (on it's own) , so I believe whatever is making this noise is the source of the electrical current draw.
The noise comes from under the hood, it sound like it's slightly on the passenger side, but not 100% certain. Since I have noticed this same noise when I get ready to start the car and hit the brake pedal, could this be related to a booster pump, or some part of the brake by wire system generating some sort of pressure?
I'm dying to get this resolved, because I can't afford another 12 hours at the repair shop without resolution, and I can't leave my car off a trickle charger for more than 24 hours or the battery goes flat.
Thanks in advance for any help.