So my brother bought a 2004 XC90 T6. We have gotten about everything working that wasn't other than the radio. The original radio (no phone/ with parking sensors) will work 100% occasionally in the morning for a few mins then its like no power, no display, no noises and doesn't ever work except the following morning. I have searched quite a bit and seen the radio/ ICM seems to have quite a bit of issues with it just powering off. I am not clear which part is which. He purchased a "radio control panel" (the part that has the buttons on it/ display). When we put it in the only thing that happens is you can hear the CD changer continually clicking.... no other sounds/ lights. This radio control panel was supposedly pulled from a working car according to the eBay seller. Is this part also called the ICM ( Infotainment control module)?

 

The two other pieces of the pie that might be relevant are the amplifier (located underneath the front passenger seat) and the actual guts of the am/fm radio (located in the overhead at the back of the trunk underneath the plastic ceiling panel). I would start by looking at the connections for those two pieces of equipment. I would also look for evidence of corrosion or water damage on the amp connections. If your brother's car had the standard clogged sunroof drains at some point then there was probably water on the passenger side footwell at some point. This also messes up the yaw rate sensor which is also underneath the passenger seat.