I have had DSP 2 & DSP 5 switches installed since the custom OS's came out. I could never get DSP 5 to work so the other day I pulled out the wheel well and verified the pins were in correctly. The DSP 2 I only am running one wire and grounding the other side of the switch, its been working for years and still works. My DSP 5 is wired per the efi instructions and it has never worked. Do I have a bad DSP 5 switxh? I bought it from one of the big diesel shops on the diesel place.