ODOMETER
DESCRIPTION
An odometer and trip odometer are standard equipment in all instrument clusters. The odometer and trip odometer information are displayed in a common electronic, blue-green Vacuum Fluorescent Display (VFD) unit. The VFD unit is soldered onto the cluster electronic circuit board and is visible through a window with a smoked clear lens located in the lower edge of the tachometer gauge dial face of the cluster overlay. The dark lens over the VFD prevents it from being clearly visible when it is not illuminated.
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 button that extends through the lower edge of the cluster lens, just right of the odometer VFD. When the trip odometer information is displayed, the word TRIP is also illuminated near the bottom of the VFD in a blue-green color and at the same lighting level as the trip odometer information.
The odometer and trip odometer distance information is stored in the instrument cluster memory. This information can be increased when the proper inputs are provided to the instrument cluster, but the information cannot be decreased. The odometer can display values up to 864,004 kilometers (536,870 miles). The odometer latches at these values, and will not roll over to zero. The trip odometer can display values up to 9,999.9 kilometers (9,999.9 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), while 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 is selected at the time that it is manufactured, and cannot be changed. If the instrument cluster has a kilometers-per-hour primary speedometer scale, the odometer/trip odometer registers kilometers; and if the cluster features a miles-per-hour primary speedometer scale, the odometer/trip odometer registers miles.
The odometer/trip odometer has a RENTAL CAR mode, which will illuminate the odometer information in the VFD whenever the driver side front door is opened with the ignition switch in the OFF or ACCESSORY positions. During daylight hours (exterior lamps are OFF) the VFD is illuminated at full brightness for clear visibility. At night (exterior lamps are ON) the VFD lighting level is adjusted with the other cluster illumination lamps using the panel lamps dimmer control ring on the left control stalk of the multi-function switch. However, a PARADE mode position of the panel lamps dimmer control ring allows the VFD to be illuminated at full brightness if the exterior lamps are turned ON during daylight hours.
The odometer/trip odometer VFD unit, the trip odometer switch, and the trip odometer switch button are serviced as a unit with the instrument cluster.
OPERATION
The odometer and trip odometer give an indication to the vehicle operator of the distance the vehicle has traveled. This indicator is controlled by the instrument cluster circuitry based upon cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Programmable Communications Interface (PCI) data bus.
The odometer and trip odometer information is displayed by the instrument cluster Vacuum Fluorescent Display (VFD) unit. The VFD will display the odometer information whenever the driver side front door is opened with the ignition switch in the OFF or ACCESSORY positions, and will display the last previously selected odometer or trip odometer information when the ignition switch is turned to the ON or START positions. The instrument cluster circuitry controls the VFD and provides the following features:
- Odometer/Trip Odometer Display Toggling - Actuating the trip odometer reset switch button momentarily with the VFD illuminated will toggle the display between the odometer and trip odometer information. Each time the VFD is illuminated with the ignition switch in the ON or START positions, the display will automatically return to the last mode previously selected (odometer or trip odometer). The VFD can be reverted to the odometer display and any currently displayed textual messages suspended by momentarily depressing and releasing the odometer/trip odometer reset switch button.
- Trip Odometer Reset - When the trip odometer reset switch button is pressed and held for longer than about two seconds with the ignition switch in the ON or START positions, the trip odometer will be reset to 0.0 kilometers (miles). The VFD unit must be displaying the trip odometer information in order for the trip odometer information to be reset.
- Communication Error - If the cluster fails to receive an electronic 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 will display error.
- Actuator Test - Each time the cluster is put through the actuator test, the VFD will step sequentially through a display of 111111 through 999999, then display the cluster software version number to confirm the functionality of each of the VFD unit segments and the cluster control circuitry.
The PCM continually monitors the vehicle speed pulse information received from the Body Control Module (BCM), then sends the proper messages to the ElectroMechanical Instrument Cluster (EMIC).
For proper diagnosis of the vehicle speed sensor, the BCM, the PCM, the EMIC, the PCI data bus or the electronic communication related to odometer/trip odometer operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.