Compass/Mini-Trip Computer

COMPASS MINI/TRIP COMPUTER
The Compass/Mini-Trip Computer (CMTC) is located in the overhead console on models equipped with this option. The Compass/Mini-Trip Computer module features a large Vacuum Fluorescent Display (VFD) screen for displaying information, and four back-lit push button function switches labeled C/T (compass/thermometer), RESET, STEP, and US/M (United States/Metric Scale).

The Compass/Mini-Trip Computer module contains a central processing unit and interfaces with other electronic modules in the vehicle over the Programmable Communications Interface (PCI) data bus network. The PCI data bus network allows the sharing of sensor information. This helps to reduce wire harness complexity, reduce internal 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.

The Compass/Mini-Trip Computer module contains six informational displays which can be displayed using the four outer buttons on the overhead console. When the vehicle is first turned ON:
- CMTC blanks the display for a half second
- Displays whatever was being viewed when the ignition was last turned OFF

The CMTC may also be integrated with the Universal Transmitter. If so, your CMTC module will have three buttons centered together between the outer four buttons. Below the three buttons are corresponding dots to indicate which button you are using.

The Compass/Mini-Trip Computer includes the following display options:

- Compass and thermometer - provides the outside temperature and one of eight compass readings to indicate the direction the vehicle is facing.
- Average fuel economy - shows the average fuel economy since the last trip computer reset.
- Trip odometer - shows the distance travelled since the last trip computer reset.
- Blank screen - the CMTC compass/thermometer/trip computer VFD is turned off.

If the vehicle is equipped with the optional Universal Transmitter transceiver, the CMTC will also display messages and an icon indicating when the Universal Transmitter is being trained, which of the three transmitter buttons is transmitting, and when the transceiver is cleared.

Data input for all CMTC functions, including VFD dimming level, is received through PCI data bus messages. The CMTC module uses its internal programming and all of its data 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 inconclusive, the use of a DRBIII scan tool and the proper Diagnostic Procedures manual are recommended for further testing of the CMTC module and the PCI data bus.

The CMTC module cannot be repaired, and is available for service only as a unit. This unit includes the push button switches and the plastic module and display lens. If any of these components is faulty or damaged, the complete CMTC module must be replaced. The incandescent bulbs used for CMTC push button back-lighting are available for service replacement.

The Compass/Mini-Trip Computer operates when the ignition is in the ON position. The VFD will display the last display before ignition was turned OFF.

The four outer buttons operate:
- STEP
- C/T - Compass/Temperature
- US/M - English/Metric
- RESET

1. STEP BUTTON
Pressing the STEP button selects one of the following 6 displays:
- Average fuel economy
- Distance to empty
- Trip odometer
- Elapsed time
- Blank Screen

2. C/T (COMPASS/TEMPERATURE) BUTTON
Pressing the C/T button selects the Compass/Temperature display.

3. US/M (ENGLISH/METRIC MEASUREMENT) BUTTON
Pressing the US/M button switches the display units between English and Metric readings.

4. RESET BUTTON
Pressing the RESET button resets the function on the display, provided that function can be reset. The functions which can be reset are Average fuel economy, Trip odometer and Elapsed time.

Global Reset - This feature allows all three displays (Average fuel economy, Trip odometer and Elapsed time) to be reset easily, by pressing the RESET button twice within three seconds with any of the screens in display. This eliminates the need to reset each display individually.

The RESET button is also used to set the variance and/or calibrate the compass. Refer to the Variance Procedure and Calibration Procedure.

For more information on the features, control functions and setting procedures for the CMTC module, see the owner's manual in the vehicle glove box.

COMPASS
While in the compass/thermometer 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 three complete circles at 5 - 8 kmh (3 - 5 mph), on level ground, in not less than forty-eight seconds. This will reorient the compass unit to its vehicle.

The compass unit also will compensate for magnetism the body of the vehicle may acquire during normal use. However, avoid placing anything magnetic directly on the roof of the vehicle. Magnetic mounts for an antenna, a repair order hat, or a funeral procession flag can exceed the compensating ability of the compass unit if placed on the roof panel. Magnetic bit drivers used on the fasteners that hold the overhead console assembly to the roof header can also affect compass operation. If the vehicle roof should become magnetized, the demagnetizing and calibration procedures found in this group may be required to restore proper compass operation.

THERMOMETER
The thermometer displays the outside ambient temperature in whole degrees. The temperature display can be toggled from Fahrenheit to Celsius by using the U.S./Metric button. The displayed temperature is not an instant reading of conditions, but an average temperature. It may take the thermometer display several minutes to respond to a major temperature change, such as driving out of a heated garage into winter temperatures.

When the ignition switch is turned to the Off position, the last displayed temperature reading stays in the Body Control Module (BCM) unit memory. When the ignition switch is turned to the On position again, the CMTC will display the memory temperature for one minute; then update the display to the current average temperature reading within five minutes.

The thermometer function is supported by an ambient temperature sensor. The sensor is mounted outside the passenger compartment near the front and center of the vehicle, and is hard wired to the Body Control Module (BCM). The BCM sends temperature status messages to the CMTC module over the PCI data bus network. The ambient temperature sensor is available as a separate service item, refer to additional information.