Ebonics213

Hello I’m new on the forum and also new to the smd products so today I tried finding the maximum distortion level on my factory head unit I followed all steps on the instructions Manuel I received with my dd1+ I wasn’t able to get any distortion or any 40hz reading on my dd1+ display what could be the issue on why this is happening I also have a loc-22 connected to my factory head unit so I could use my bass amp could the loc-22 be the issue on why I’m not getting any reading on the dd1+ any info would help thank you