MODULE-ELECTRONIC OVERHEAD
DESCRIPTION
The Electronic Overhead Module (EOM) is located in
the overhead console (7) and consists of the following
components:
•
Compass
mini-trip
computer
(on
vehicles
equipped with this option)
•
Vacuum-Fluorescent Display (VFD) (6)
•
Push button function switches (1, 2, 3, 4 and 5)
The EOM contains a central processing unit and inter-
faces with other electronic modules in the vehicle on
the Controller Area Network (CAN) data bus. The CAN
data bus allows the sharing of sensor information. This
helps to reduce wire harness complexity, reduce inter-
nal controller hardware, and reduce component sensor
current loads. At the same time, this system provides
increased reliability, enhanced diagnostics, and allows
the addition of many new feature capabilities. If any of
the components of the EOM are damaged or inopera-
tive the entire EOM must be replaced,.
The EOM provides several electronic functions and features. Some of the functions and features that the EOM sup-
ports and/or controls, include the following display options:
•
Compass and temperature - provides the outside temperature and one of eight compass readings to indicate
the direction the vehicle is facing.
•
Trip odometer (TRIP ODO) - shows the distance travelled since the last trip computer reset.
•
Average fuel economy (AVG ECO) - shows the average fuel economy since the last trip computer reset.
•
Distance to empty (DTE) - shows the estimated distance that can be travelled with the fuel remaining in the
fuel tank. This estimated distance is computed using the level of the fuel in the tank and a weighted average
of long term and recent Average Fuel Economy.
•
Elapsed time (ET) - shows the accumulated ignition-on time since the last trip computer reset.
•
Blank screen - the compass mini-trip VFD is turned off.
The ambient temperature sensor is hard wired to the Front Control Module (FCM). The instrument cluster, also
known as the Cab Compartment Node (CCN) averages and filters the ambient temperature signal and supplies it to
other modules on the CAN data bus. Data input for all other compass mini-trip computer functions, including VFD
dimming level, is received through CAN data bus messages. The maximum temperature displayed is 66°C (140° F).
It could take several miles for the accurate temperature to be displayed as the CCN filters out heat from the engine
compartment.
The EOM uses its internal programming and all of these inputs to calculate and display the requested data. If the
data displayed is incorrect, perform the self-diagnostic tests as described in this group. If these tests prove incon-
clusive, the use of a scan tool and the proper Diagnostic Procedures Information are recommended for further test-
ing of the EOM and the CAN data bus.
The EOM cannot be repaired, and is available for service only as a unit. This unit includes the push button
switches, the Universal Garage Door Transmitter and the plastic module and display lens. If any of these compo-
nents is inoperative or damaged, the complete EOM must be replaced, (Refer to 8 - ELECTRICAL/OVERHEAD
CONSOLE/COMPASS/MINI-TRIP COMPUTER - REMOVAL).
COMPASS
While in the compass/temperature mode, the compass will display the direction in which the vehicle is pointed using
the eight major compass headings (Examples: north is N, northeast is NE). The self-calibrating compass unit
requires no adjusting in normal use. The only calibration that may prove necessary is to drive the vehicle in one or
two complete circles, on level ground, in not less than 16 seconds. This will reorient the compass unit to its vehicle.
8M - 18
OVERHEAD CONSOLE - SERVICE INFORMATION
ND