I had a 52 plate S60 2.0 T SE, with the hu-803 sound system.
I now have a 53 plate S60 D5 S with the Hu-603 system

I read up a bit and swapped the 803 into my D5, changing all speakers, amp and lead, AND also the AC control panel to keep the colour matched.

I have good sound as before but the following problems:

SRS airbag fault message on display (this may have happened when I accidentally turned on the ignition in mid installation?)

Rear demister light not on, can't see if it's working yet

STC button on, but won't turn off

Alarm button next to it on, but won't turn off

Audio controls on steering wheel not working

Does anyone have an idea what caused this and how to fix it. Everything else appears to work fine so far.

Any help would be much appreciated, thanks.