I have a 2005 XC90 with a 2.5L Turbo, 2 wheel drive. Recently it would not start, nothing when I turned the key. Thought it might be the battery, so charged it overnight and it started right up. I then had the charging system checked. All appeared good except there was a significant power drain on the battery. Let it sit a few days and when I went to start it, again nothing. Charged overnight. When I went to start, it started right up. Let it run a bit, then it quit. I noticed a clicking sound in the right rear door, which appeared to becoming near the child lock area. Thinking this may be related to the power drain, has anyone experienced this? If so, what was your solution?

 

I'm experiencing the exact same issue. Were you ever able to resolve this?