Odometer - Operation

OPERATION

The odometer and trip odometer give an indication to the vehicle operator of the distance the vehicle has traveled. The engine hours give an indication of the cumulative engine-on time. 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 Controller Area Network (CAN) data bus.

The odometer, trip odometer and engine hours information is displayed by the instrument cluster odometer/trip odometer Vacuum Fluorescent Display (VFD). The VFD displays the odometer information whenever any door is opened with the ignition switch in the OFF or ACCESSORY positions, and displays the last previously selected odometer or trip odometer information when the ignition switch turns 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 toggles 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 automatically returns to the last mode previously selected (odometer or trip odometer).
- Engine Hours Display Toggling - When the trip odometer reset switch button is pressed and held for longer than about six seconds with the ignition switch in the ON position and the engine speed message from the PCM is zero, the trip odometer information momentarily displays, then the engine hours information displays. The VFD must display the odometer information when the trip odometer reset switch button is pressed in order to toggle to the engine hours display. The engine hours remains displayed for about 30 seconds, until the engine speed message is greater than zero, or until the ignition switch turns to the OFF position, whichever occurs first.
- 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 resets to 0.0 kilometers (miles). The VFD must display the trip odometer information in order for the trip odometer information to be reset.
- GASCAP Message Display - On vehicles manufactured with a United States country code, each time the cluster receives an electronic message from the PCM indicating a monitored leak in the evaporative emissions system, the cluster replaces the displayed odometer/trip odometer value with the textual message, GASCAP. This message serves as a reminder to the vehicle operator to check that the gas cap is properly installed and tightened, but could also indicate another source of air leakage in the on-board evaporative and vapor recovery emissions systems. Unless the leak is corrected, this message latches and remains displayed during the current and each subsequent ignition cycle until the trip odometer reset button is pressed and released momentarily, which reverts the display to the odometer/trip odometer information that was last displayed for the remainder of that ignition cycle. Once the source of a leak has been corrected, either momentarily pressing the trip odometer reset button or cycling the ignition switch unlatches the message and return the odometer/trip odometer to normal operation.
- NO-FUSE Message Display - Each time the cluster receives an electronic message from the Front Control Module (FCM) indicating the Ignition-Off Draw (IOD) feed for the cluster is an open circuit, the cluster replaces the displayed odometer/trip odometer value with the textual message, NO-FUSE. This message indicates that the IOD fuse is missing, blown or that the IOD feed circuit is ineffective. Unless the problem is corrected, this message latches and remains displayed during the current and each subsequent ignition cycle until the trip odometer reset button is pressed and released momentarily, which reverts the display to the odometer/trip odometer information that was last displayed for the remainder of that ignition cycle. Once the problem has been corrected, either momentarily pressing the trip odometer reset button or cycling the ignition switch unlatches the message and return the odometer/trip odometer to normal operation.
- Ambient Temperature Display - On vehicles that are not equipped with the optional Electronic Vehicle Information Center (EVIC), each time the cluster receives an electronic ambient temperature message from the FCM, the cluster replaces the displayed odometer/trip odometer value with the ambient temperature value. This value displays and updates during the current ignition cycle until the trip odometer reset button is pressed and released momentarily, which reverts the display to the odometer/trip odometer information that was last displayed for the remainder of that ignition cycle.
- Communication Error - If the cluster fails to receive an electronic distance message during normal operation, it holds and displays 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 turns to the ON position, it displays the last distance value stored in the cluster memory. If the cluster is unable to display distance information due to an error internal to the cluster, the VFD displays Error.
- Self Test - Each time the cluster is put through the self test, the odometer VFD displays all of its segments simultaneously, then step through each character segment individually during the VFD portion of the test to confirm the functionality of the VFD and the cluster control circuitry.

The PCM continually monitors the vehicle speed pulse information received from the Vehicle Speed Sensor (VSS) and engine speed pulse information received from the crankshaft position sensor, then sends the proper messages to the instrument cluster, also known as the Cab Compartment Node (CCN). For further diagnosis of the odometer/trip odometer or the instrument cluster circuitry that controls these functions, Testing and Inspection.

Use a diagnostic scan tool for proper diagnosis of the VSS, the crankshaft position sensor, the PCM, the CCN, the CAN data bus or the electronic communication related to odometer/trip odometer operation. Refer to the appropriate diagnostic information.