The kit fitted to my previous 350 when new by the supplying Nissan Dealer had leads, which when you pulled the individual sensor out, were capable of being detached from the cable (one of the four) going to the control unit. In that way, by testing with another sensor that was working OK you could tell if it was the sensor (or that small section of supply cable) that was not working, or there was a fault in the cable going to the control unit, or the unit itself.