You may need to go to the connector on the firewall. I found these pictures on another website showing the pinout and wires spliced into the connector.

Name: pinout1.jpg Views: 19123 Size: 171.7 KB

Name: ip connector.jpg Views: 3431 Size: 121.0 KB

Name: ip connector 2.jpg Views: 4075 Size: 155.0 KB