The most common cause of a new radio with no sound, is having the "infinity" or the premium sound system in your van. Each of the speakers has it's own amplifier. Problem is, that an aftermarket radio won't be setup to tell the amplifiers to turn on. No amps turned on, no sound. Usually it's hooking up the blue "amplifier" or the blue/white "power antenna" wires to one of the wires on the original van side of the harness. I don't recall what color. There is several threads about how to power on the factory amplifiers. I'll do a bit of searching tonight when I have more time.
2005 Kia Sorento LX 4x4 44,000mi
2003 Chrysler T&C Limited 3.8l AWD 145,000mi Traded in 9/14/11
2000 Dodge Stratus ES v6 179,000 sold 7/2011