The EGO (exhaust gas oxygen) sensors are on the exhaust, shockingly enough. If your car was made before 2003 (I think) you'll need to get a special EGO sensor that can send a narrowband signal to the engine computer AND send a wideband signal to your gauge. If your car was made 2003 or after (again, I think) then you already have a wideband EGO sensor and so the gauge can connect directly to it.This probably is out there somewherebut I cant find it. I got a C2 Air/fuel ratio wideband gauge now I need instructions on how do I conect the electrical part, and where is the 02 sensor.Tahnks