Vehicle is a 2005 Volvo S40. I have been having problems with my alarm going off randomly, so I just stopped locking my door. Well, now my battery has been completely drained. I bought a new siren control module to replace the one not working, but before I attempt to tear something apart I would like some confirmation on where to start. I have not had the best luck finding information on this model. The only thing I did find was somebody said it's under the plastic cowl under the windshield, one said passenger side, but not sure if they were talking about a European model or US, I am in the US. If anyone knows the correct location or has any documentation or a link it would be much appreciated. Thanks!

  • You sure its not just the the door ajar sensor bad? Id suspect that first and then maybe issue stemming from CEM, – narkeleptk Jun 23 '20 at 15:38
  • Would the door ajar sensor cause the battery to drain? I am basing my theory on the Siren alarm just on the tons of stuff I have read, but I would like to be able to find it to check if that is or is not the issue also to make sure I got the right part. – shotgunn66 Jun 23 '20 at 16:19
  • Welcome to Motor Vehicle Maintenance & Repair! It sounds as if you might have two issues going on here. I'd check to ensure the battery is up to snuff, then figure out where the drain is coming from. I doubt the sensor itself is going to cause the drain unless it wasn't working and the door was seen as ajar at all times. If so, though, the dome light would be on (or there would be other indicators). – Pᴀᴜʟsᴛᴇʀ2 Jun 23 '20 at 16:21
  • I do think the battery might be a part of the issue as far as the drain in concerned, because the siren issue has never cause a battery drain that rapidly, However I would still like to look at that alarm sensor, anyone know where its for sure located? – shotgunn66 Jun 23 '20 at 16:27
  • @shotgunn66 If the door ajar switch is bad it makes the car think the door is opening and closing randomly. When the door is signaled as opens the can network comes online and you also have things like lights coming on. So yes a bad ajar switch could easily cause battery drain and random alarms. – narkeleptk Jun 23 '20 at 21:31

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