Remove the touch pad and try touching the two wires to each other.
Any vehicle that has a touch pad to open the liftgate also has some sort of mechanical way to open it as well (in case the battery is dead). For your vehicle the process is as follows:
Emergency Release for Opening
1. Remove the trim plug to expose the access hole in
the trim panel. The access hole is located on the
inside of the liftgate.
2. Use a tool to reach through the access hole in the
3. Pry the left release lever up to the unlock position.
Pry the right release lever up to unlatch the liftgate.
4. Reattach the trim plug.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)