Body Control System Description and Operation: Odometer
WARNING: This page is about a different car, the 2005 Saturn L300. However, it is still accessible from the selected car via links, so may be relevant.
The body control module (BCM) calculates vehicle mileage from rolling count data sent to the BCM by a controlled area network (CAN) message from the engine control module (ECM) (L81) or a class 2 message from the powertrain control module (PCM) (L61). The BCM sends the mileage data to the cluster over serial data to display the vehicle mileage. The actual mileage is located in the BCM. All calculations for odometer are performed in the BCM.