Here is the pin out info for all Suzuki Grand Vitara vehicles from 2006-later (currently 2013, but later model years of the same body type will be exactly the same, if there are any). I posted this on a Suzuki forum, but I thought it might be useful here as well:
PIN 1 – Constant battery voltage (White)
PIN 2 – Panel illumination signal from lighting switch (+ On/Off) (Red w/yellow stripe)
PIN 3 – Left front speaker (+) signal, left tweeter (+) signal, center speaker (+) signal (Black w/white stripe)
PIN 4 – Right front speaker (+) signal, right front tweeter (+) signal, center speaker (+) signal (Grey w/green stripe)
PIN 5 – Left rear speaker (+) signal (Blue)
PIN 6 – Right rear speaker (+) signal (Blue w/black stripe)
PIN 7 – Woofer speaker (+) signal (Red w/white stripe)
PIN 8 – (empty)
PIN 9 – Ignition/ACC power input (White w/black stripe)
PIN 10 – Power feed for antenna amplifier (White w/blue stripe) Note: Radio reception will be poor unless connected
PIN 11 – Ground/earth (Black)
PIN 12 – Illumination signal from BCM (-) (Red w/green stripe) Note: This connection is likely not needed
PIN 13 – Left front speaker (-) signal, left tweeter (-) signal, center speaker (-) signal (Brown w/white stripe)
PIN 14 - Right front speaker (-) signal, right front tweeter (-) signal, center speaker (-) signal (Pink w/green/stripe)
PIN 15 – Left rear speaker (-) signal (Light green w/black stripe)
PIN 16 – Right rear speaker (-) signal (Grey w/red stripe)
PIN 17 – Woofer speaker (-) signal (Black w/blue stripe)
PIN 18 – BCM speed pulse signal (Blue w/black stripe)
PIN 19 – Steering wheel remote (+) signal (Purple)
PIN 20 – Steering wheel remote (-) signal (Pink w/black stripe)
The antenna is a standard round-style plug, a direct fit for most aftermarket head units.