One has to be careful wiring this thing to the car. Canable has 4 terminals: canh, canl, ground, +5v. Only canh and canl need to be wired to the OBD2 connector if that's what you are doing. I initially connected canable ground to obd2 signal/chassis ground and that really made me and my car freak out. It somehow recovered after throwing a couple of error codes.