Principles of Operation: Notes

WARNING: This page is about a different car, the 2010 Lincoln MKX and 2010 Ford Edge. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: The Smart Junction Box (SJB) is also known as the Generic Electronic Module (GEM).

NOTE: Whenever a network message is suspected as missing and confirmed by a missing message DTC (U-code), it is important to look for other symptoms that may also be present in the Instrument Cluster (IC) and throughout the vehicle. Once a DTC is set in the IC , it may be helpful to review the complete message list available in MODULE COMMUNICATIONS NETWORK to see what other modules also rely on the same message and run the self-test for those modules. If the message is missing from other modules, the same DTC may also be set in those modules. Confirmation of missing messages common to multiple modules may indicate that the originating module is the source of the concern or the communication network may be experiencing some problems.

The IC utilizes a microprocessor to control the gauge, indicator, message center and warning chime functions. Data is sent to the IC over the High Speed Controller Area Network (HS-CAN), the Medium Speed Controller Area Network (MS-CAN) bus lines and through hardwired circuitry from individual components. The IC uses each input to output an action to the gauges or indicators.

It is very important to understand:

where the input originates.
all the information necessary in order for a feature to operate.
which module(s) receive(s) the input or command message.
does the module which received the input control the output of the feature, or does it output a message over the communication network to another module.
which module controls the output of the feature.