Normal Operation
WARNING: This page is about a different car, the 2005 Mercury Montego, 2005 Ford Freestyle, and 2005 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
The restraints control module (RCM) monitors the HS-CAN for messages from the instrument cluster module and the powertrain control module. If the RCM detects a communication bus fault or missing messages, it will store diagnostic trouble code (DTC) U1900 in memory.