I was just looking through my manual trying to find the answer to the March/April quiz and found a reference to cleaning the underbody.

According to the Isuzu manual you CAN spray the underbody with water to remove dust, dirt, de-icing agents, salt, etc. They recommend that you do it at least once a year (in the spring) and state no precautions concerning any of the electrical connections located along the undercarriage.