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Trip Computer: Description and Operation

COMPASS/MINI-TRIP COMPUTER (CMTC)
The Compass/Mini-Trip Computer (CMTC) is in the overhead console. It displays the following information:
- Compass direction
- Current outside temperature
- Elapsed Time (ET)
- Distance To Empty (DTE)
- Average Fuel Economy (AVE ECO)
- Instantaneous Fuel Economy (ECO)
- Trip Odometer (ODO)

All of the information required by the CMTC except the ambient temperature and compass direction is transmitted over the CCD bus.

The CMTC can perform an independent self-test. This can be accomplished by using either the DRB or pressing both US/M and STEP buttons and then turning the ignition key ON. All segments of the CMTC should light while the CMTC checks its internal function. If there are internal failures, the CMTC will display "FAIL." If there is a problem with the CCD communication, the CMTC will display "CCD." Refer to the "Compass/Mini-Trip" for further diagnosis.

Compass
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). It does not display the headings in actual degrees.

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, on level ground, in not less than 48 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 assembly to the roof header can also affect compass operation. If the vehicle roof should become magnetized, demagnetizing and calibration may be required to restore proper compass operation. See Compass Calibration or Compass Demagnetizing in the Service Procedures for these procedures.

The compass, trip computer, and thermometer display module cannot be repaired, and is only available for service as a unit. If faulty or damaged, the complete module must be replaced. The push button (Step and U.S./Metric) switch module is serviced separately.

Setting The Compass
The compass/mini-trip module is self-calibrated and requires no adjustment. The word CAL will be displayed to indicate that the compass is in the fast calibrating mode. CAL will turn OFF after the vehicle has gone in three complete circles without stopping, in an area free of magnetic disturbance.

If the module displays the temperature while the compass is blank, or displays a false reading, the vehicle must be demagnetized.

If the compass still goes blank after the vehicle is demagnetized, the compass/mini-trip module must be replaced.

Setting The Variance:




Setting The Compass Variance
Variance is the difference between magnetic north and geographic north. To determine the variance for the area you are in, refer to the zone map. The number shown for your area is the variance number for your area.

1. Set the compass/mini-trip console to compass/ temperature mode.
2. Press and hold down both the US/METRIC button and the STEP button for 5 seconds.
3. The VAR light will come ON and the last variance setting will be displayed.
4. Enter the correct variance number by pressing the US/M button.
5. Press the STEP button to set the zone number and resume normal operation.

NOTE: DO NOT ATTACH ANY MAGNETIC DEVICE SUCH AS A MAGNETIC CB ANTENNA TO THE VEHICLE. THIS CAN CAUSE THE COMPASS TO GIVE FALSE READINGS.

Thermometer
The thermometer displays the outside ambient temperature. The temperature display can be changed from Fahrenheit to Celsius using the U.S Metric button, located just rearward of the display module. 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 thermometer unit memory. When the ignition switch is turned to the ON position again, the thermometer will display the memory temperature if the engine coolant temperature is above about 52 °C (125 °F). If the engine coolant temperature is below about 52 °C (125 °F), the thermometer will display the actual temperature sensed by the ambient temperature sensor. The thermometer temperature display update interval varies with the vehicle speed.

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 module. The ambient temperature sensor is available as a separate service item.

The thermometer, compass, and trip computer display module cannot be repaired, and are only available for service as a unit. If faulty or damaged, the complete module must be replaced. The push button (Step and U.S./Metric) switch module and ambient temperature sensor are serviced separately.

Trip Computer
A mini trip computer is available on this model to provide several electronic functions and features. The trip computer contains a central processing unit and interfaces with other modules in the vehicle on the Chrysler Collision Detection (CCD) data bus network.

The CCD 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.

Some of the functions and features that the trip computer supports and/or controls, include the following display options:
- Compass and temperature
- Trip Odometer (ODO)
- Average Fuel Economy (AVG ECO)
- Instant Fuel Economy (ECO)
- Distance To Empty (DTE)
- Elapsed Time (ET)
- Blank display.

Momentarily depressing and releasing the Step button when the ignition switch is in the ON position will cause the overhead console display to step sequentially through the listed display options. Momentarily depressing and releasing the U.S./Metric button toggles the display between U.S. and Metric measurements.

The push button (Step and U.S./Metric) switch module in the overhead console is hard wired to the trip computer. The compass flux-gate unit is integral to the trip computer, compass, and thermometer display module unit. Data input for all other trip computer functions is received through CCD data bus messages. The trip computer uses its internal programming and all of these inputs to calculate and display the requested data. If the data displayed is incorrect, see Trip Computer, Compass, and Thermometer Display Module - Self-Diagnostic Test in the Diagnosis and Testing. If these tests prove inconclusive, the use of a DRB scan tool and the proper Diagnostic Procedures are recommended for further testing of the trip computer and the CCD data bus.

The trip computer, compass, and thermometer display module cannot be repaired, and is only available for service as a unit. If faulty or damaged, the complete module must be replaced. The push button (Step and U.S./Metric) switch module is serviced separately.

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