Section 307 (Navigation/Telecommunication (Service Information)): Operation: Navigation
The optional navigation system is active whenever the Radio Receiver Module (RRM) (also known as the radio or the head unit) electronic display is powered On. If a navigation system menu or map isn't being actively displayed, the system is still operating in the background. The menu, map or route that was active when the RRM was powered Off along with all other user-relevant information is saved in nonvolatile memory by the navigation module for display again the next time the RRM is powered On and the navigation system is selected.
Once a destination is selected, the navigation system uses information from stored map data to quickly calculate a route. As the vehicle is driven along that route, the vehicle operator is guided with visual displays and voice prompts. Any variances from that route will cause the navigation system to automatically recalculate and deliver a revised route to the chosen destination.
All vehicles have their original map and Points-Of-Interest (POI) data stored in nonvolatile flash memory integral to the navigation module integral and internal to the RRM. Updated map and POI data as well as updated navigation software for these vehicles can be uploaded to the system using Universal Serial Bus (USB) media. The originally installed data is based upon the market for which the vehicle was manufactured. Navigation software updates are also uploaded to the system using USB media.
The Global Positioning System (GPS) receiver of the navigation module is capable of acquiring and tracking GPS signal inputs through the roof-mounted combination antenna from numerous satellites simultaneously to calculate and display the position and direction of the vehicle. However, when access to satellite signals is blocked by bridges, tunnels or other obstacles, the navigation module relies upon Dead Reckoning (DR) to aid in calculating vehicle position and direction. The navigation module uses pulse signals from the wheel speed sensors, a Reverse gear indicator input and an internal electronic gyroscope sensor to provide DR vehicle position and direction calculations to supplement GPS satellite signals.
The user input mechanism for the navigation system is the RRM touchscreen. For safety reasons some input, editing and setting features of the navigation system are restricted when the vehicle is in motion or when a hands free phone call is active. This includes many features that require touchscreen inputs.
The navigation module receives electronic message inputs within the RRM over the Controller Area Network - B (CAN-B) data bus; however, the RRM is not a CAN gateway. All electronic message outputs of the navigation module and the RRM are carried over the CAN-B data bus. When the RRM monitors a problem in any of the navigation system antenna circuits, it stores a fault code or Diagnostic Trouble Code (DTC) in its memory circuit. The external combination antenna may be diagnosed separately from the RRM.
The hard wired circuits between components related to the RRM and the navigation system may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, details of wire harness routing and retention, connector pin out information and location views for the various wire harness connectors, splices and grounds.
However, conventional diagnostic methods will not prove conclusive in the diagnosis of the RRM or the electronic controls and communication between modules and other devices that provide some features of the navigation system. The most reliable, efficient and accurate means to diagnose the RRM or the electronic controls and communication related to navigation system operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.