Doesn't matter if the trolling motor is on or off does it all the time at all depths not just 15' of water. Also doesn't matter if the other sonar unit is on or off, originally when it worked the other sonar could be on and it worked fine, now it doesn't matter, it just acts the same. I understand the DI won't work with the US2 I was trying a different transducer as I was told to do, it malfunctions with the correct transducer as well. I'm not sure what the imaging frequency is set to right off I'll have to check. Thank you for the response.