I have a 4 amp drain on my XC90 electrical system. Hooked up a monitor and removed every fuse one at a time. The drain went away when four fuses were removed. The four fuses are numbers 2(audio amplifier), 20 (infotainment system), 27 (central electronic module), and 37(navigation system/dvd player). I do not have a navigation system. I have a secondary radio, however I believe the problem started before the new radio. Any idea of what could be causing this?

One other issue, that I am not sure is related, is with the passenger side window. When I try to raise the window it goes up to the top and then back down but not all the way to where it started. In order to close the window completely I have to hold the up button for a few seconds after the window is completely closed.

 

I have a similar problem and suspect the CEM (central electronic module) to be defective. It could well be some defective sensor also, I'm just guessing here. Now I see you received no comments on your post, did you manage to find what caused the drain? From the manual I find that fuses are divided into 4 separate groups, and every fuse list starts with fuse number 1. When you say CEM fuse is number 27, which group is that? Is your number from the VIDA diagnostic system (which I don't have access to)?

 

The local dealer looked at my XC90 as did two different independent mechanics. None of them have been able to find out why my battery drains. I know there is a 4 amp drain for a short period when you shut the motor off, but it still continues to drain so I put a battery tender to keep it charged.


The fuse 27 came from the diagram on the owners manual.

 

I'm almost certain now. I finally found an independent mechanic who would remove the CEM 0f my XC90 01/2005, open it in my presence and check for corrosion on one of the two circuit boards. Gaze and behold, there were substantial corrosion on one of the two boards, where what appeared to be the CPU some of the pins or riser leads were severely corroded. He cleaned it with some spray and a cloth and followed up with pressurized air from a distance.

My fears that that treatment would cause more damage proved unfounded and the car doesn't throw any error messages any more. Now my main concern is that the protective spray might not be sufficient and he didn't tighten the plastic box nor did he seal it any better. On the other hand, there were no signs of water intrusion anywhere except for a few spots on one of the two boards. So it could well be that Volvo installed corroded boards in the first place, which might explain why there has been so many mystical different error messages over the ten years I've had the car. But it doesn't explain why no Volvo repair guy has considered that the CEM might be defective. If you can't trust the computer, who then can you trust?