Normal Operation
WARNING: This page is about a different car, the 2006 Mercury Milan, 2006 Lincoln Zephyr, and 2006 Ford Fusion. However, it is still accessible from the selected car via links, so may be relevant.
The oil pressure switch is a normally open switch that is hardwired to the smart junction box (SJB) through circuit CMC24 (GY). When the oil pressure is within normal ranges, the oil pressure switch closes, grounding the signal to the SJB. The SJB then sends a command signal to the instrument cluster over the communication network, to turn off the low oil pressure warning indicator. When engine oil pressure is low, the oil pressure switch opens, removing the ground to the SJB. The SJB sends a low oil pressure command to the instrument cluster over the communication network to illuminate the low oil pressure warning indicator.