Driver Information Center (DIC) Description and Operation: Odometer

The instrument cluster displays the vehicle odometer in the driver information center. The ECM send a distance rolling count message on GMLAN to the body control module (BCM). The BCM uses this information to calculate the vehicle odometer. This odometer value is then sent to the instrument cluster on GMLAN. The instrument cluster does not calculate the odometer. The odometer displays miles or kilometers as selected in the Units menu.

The odometer value is stored in multiple modules. The instrument cluster is a secondary storage module for the odometer, while the BCM is the primary storage and accumulator.

In addition to saving the car's odometer reading, the combi instrument and BCM save the VIN. Software checks are run to make sure that these modules and their saved odometer information cannot be moved or transferred between different vehicles.

If the VINs do not match, the instrument cluster will go into an error mode and display "- -" (dashes). If the VIN mismatch exists over a calibrated distance, the instrument cluster will "lock" the odometer display and only show dashes, even if the VIN mismatch is subsequently correct. The only way to clear or "unlock" the instrument cluster is to run a BCM programming event using SPS.