I've had my 2003 C240 wagon for about a year now and I've run into a weird issue with it. Every now and then, when I shut off my car, the stereo and subwoofer amp stay powered on. And this is the weird part - I think it has something to do with my SRS system? I start my car right after this happens and I get a message on the dash screen that says SRS, and the SRS light also comes on. But the message clears after a few seconds and the light turns off shortly after the screen message. Usually, if I continue to drive around for a little bit and shut off my car, the issue is gone. I've also found that pulling any of the fuses for the SRS control module while the car is off will power down my stereo and sub amp like they're supposed to when the car is off (I haven't driven with the fuse pulled, just when I park at work or home to make sure the battery doesn't drain because of my audio system). Has this happened to anyone? If so, what is the fix for this? I'm thinking possibly a new SRS control module but I wanted to check here first.

Unrelated (or it might actually be related), a few months ago on a road trip, I was driving on the interstate and I suddenly lost power steering, the car started overheating, and more (pretty much everything that happens when the car loses its serpentine belt). I was luckily just entering a small town as this happened, I pulled off to a parking lot and found out my serpentine belt had flown off because my idler pulley had pretty much melted from the inside out and was no longer on the bearing/pulley assembly. There were only 2 auto parts stores in this small town, and one had the pulley assembly and the other had the belt, so I got it fixed pretty quick. I continued to have a message about my alternator/battery, and that I should go to the shop (I knew it was because my alternator had stopped working during the incident and my battery was probably drained a little). I got that message reset but now I've been experiencing the SRS issue. Could this have fried or damaged my SRS module, but I'm just now seeing the issue months after?

Any help is appreciated!

 

I doubt it's related to the pulley failure. Without reading SRS and audio codes it's hard to tell what's going on. I would look at whatever circuit or fuse is used by both the audio and SRS? Does your wagon have a Bose audio system with the amp and sub built into the right side of the trunk? One problem I encountered on my C320 wagon was water intrusion from window seal leak directly above the amp caused corrosion and eventually killed the amp.

 

I have an aftermarket audio system with the amp mounted to the back of the rear seat. I pulled the fuse for the audio system, and it shut off. I put the fuse back in and the system turned back on (while my car was off). I did the same thing with the SRS control module fuse and the audio system turned off on removal and back on when I put the fuse back in. With the SRS fuse removed, I started the car and the audio system worked normally (powered on at start and turned off at shut down). Should I take it to a shop to get the fault codes read (if there are any)? Or can I get the SRS module reset at a dealer?