I was wondering if anyone could help me with a problem I'm having. Yesterday I installed a boost and a knock gauge in my 86 GN. When I finished and started my car, the speedometer would light up (digital dash), but it won't register any speed. Also my service engine soon light is on (I'm assuming this is because my speedometer isn't working?). I rechecked all of my work and it looks like everything is properly installed, but I can't get it to work. Any help is greatly appreciated.