It could be something other than power steering stemming from off road incident. Have you checked to see if the there is any damage to power steering components or the front suspension?
I assume the fluid is full, no one has added fluid that is not compatible and there are no screeching noises when you turn the wheel lock to lock. If that is the case I would remove the PS cap with the engine running and see if the fluid is circulating.
This following link may be helpful:
RealOEM.com * Diagram Selection