AUX and USB

[Talifer]

Hi, first time poster, been browsing through this forum for a bit and there are some information gems in here ;)

I just wondered if anyone could shed some light on my dealer installed in car entertainment.

I used to own an '08 Yaris TR which came with the handy aux port next to the hand brake, this worked nicely with my iTouch but I never really used it too often (the wife drove the car mainly).
As the "all new Yaris" models were about to come out, I took advantage of the dealers trying to get rid of the old models and upgraded to a '11 Yaris T Spirit.
This new model has built in Sat Nav, so a TNS410 Tomtom as far as I can tell?
It also now has 2 sockets near the hand brake, the AUX and a USB. I have been able to use the USB to play music from a memory stick (although it does not like my HTC Sensation XE acting as a drive for some reason), so it appears to be connected up in some way but I have failed to get anything from the AUX port, using the same cable I used in the old Yaris (though not the iTouch but my HTC phone). The Tomtom unit and enclosure itself makes no mention of aux, neither does the Tomtom manual, only iPod connectivity, so now I'm wondering is this even suppose to work as it did before? I was expecting that when I connected a device up to the aux port that pressing source on the unit would eventually cycle to AUX, but I've never seen this.

Anyone know what should happen before I go off and tamper with it?