Here is what I got back from Customer service:

Thank you for contacting Humminbird Customer Service. The transducer that came with your unit is the only one that will work with your unit, there is no upgrade for the DI transducer. The SI units are the units with the jigging mode. You can send in your transducer for repair and they will test it. We would recommend adjusting the sensitivity to see if this will help pick up the jig.

Rickie--Do you know for sure?