Odometer: Description and Operation

An odometer and trip odometer are standard equipment in all instrument clusters. The odometer and trip odometer information are displayed in a common electronic Vacuum-Fluorescent Display (VFD), which is centered on the lower edge of the instrument cluster and visible through a small window cutout on the instrument cluster overlay. However, the odometer and trip odometer information are not displayed simultaneously. The trip odometer reset switch on the instrument cluster circuit board toggles the display between odometer and trip odometer modes by depressing the odometer/trip odometer switch knob that extends through the lower edge of the cluster lens, just right of center. Both the odometer and trip odometer information are stored in the instrument cluster memory.

The odometer can display values up to 999,999 kilometers (999,999 miles) before it rolls over to zero. The trip odometer can display values up to 999.9 kilometers (999.9 miles) before it rolls over to zero. The odometer display does not have a decimal point and will not show values less than a full unit (kilometer or mile), the trip odometer display does have a decimal point and will show tenths of a unit (kilometer or mile). The unit of measure for the odometer and trip odometer display is not shown in the VFD. If the instrument cluster has a speedometer with a primary scale in kilometers-per-hour, a "KM" is printed on the cluster mask next to the VFD to indicate the odometer unit of measure. During daylight hours (exterior lamps OFF) the VFD is illuminated at full brightness for clear visibility. At night (exterior lamps are ON) an Analog/Digital (A/D) converter on the instrument cluster circuit board converts the analog panel lamps dimmer rheostat input from the headlamp switch to a digital dimming level signal for controlling the lighting level of the VFD. The VFD is serviced as a unit with the instrument cluster.

The odometer and trip odometer give an indication to the vehicle operator of the distance the vehicle has traveled. This gauge is controlled by the instrument cluster circuit board based upon the cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Chrysler Collision Detection (CCD) data bus. The odometer and trip odometer information is displayed by the instrument cluster Vacuum-Fluorescent Display (VFD), and the VFD will not display odometer or trip odometer cluster information after the ignition switch is turned to the OFF position. The instrument cluster circuitry controls the VFD and provides the following features:
- Odometer/Trip Odometer Display Toggling - Actuating the trip odometer reset switch momentarily with the ignition switch in the ON position will toggle the VFD between the odometer and trip odometer display. Each time the ignition switch is turned to the ON position the VFD will automatically return to the mode (odometer or trip odometer) last displayed when the ignition switch was turned to the OFF position.
- Trip Odometer Reset - When the trip odometer reset switch is pressed and held for longer than about two seconds will reset the trip odometer to 000.0 kilometers (miles). The VFD must be displaying the trip odometer information in order for the trip odometer information to be reset.
- Message Failure - If the cluster fails to receive a distance message during normal operation, it will hold and display the last data received until the ignition switch is turned to the OFF position. If the cluster does not receive a distance message within one second after the ignition switch is turned to the ON position, it will display the last distance message stored in the cluster memory. If the cluster is unable to display distance information due to an error internal to the cluster, the VFD display will be blank.
- Actuator Test - Each time the cluster is put through the actuator test, the VFD will display all of each number (0 through 9) in two second steps to confirm the functionality of the VFD and the cluster circuitry.

The PCM continually monitors the vehicle speed sensor, then sends the proper distance messages to the instrument cluster. For further diagnosis of the odometer/trip odometer or the instrument cluster circuitry that controls these functions, (Refer to INSTRUMENT CLUSTER - DIAGNO515 AND TESTING). For proper diagnosis of the PCM, the CCD data bus, or the message inputs to the instrument cluster that control the odometer/trip odometer, a DRB III scan tool and the appropriate diagnostic information are required.