Odometer refers to the instrument located in the dashboard to measure the speed driven.
The odometer records the total distance the vehicle has traveled. It is composed of a row of numbers, usually located in the speedometer, The odometer operates by a pair of gears from the speedometer shaft. Its motion is carried through the gears to the mileage or kilometer number rings. These turn to show the distance traveled by the vehicle.
Some vehicles have an electronically d river speedometer and odomter. A vehicle speed sensor or VSS on the transmission output shaft sends vehicle speed signals through wiring to the speedomter. This eliminates the speedometer cable. The speed signals to operate a small electric stepper motor that turns the odometer number rings.
Vehicles with an electronic instrument cluster have a digital speedometer and odometer display. When the key is turned off the body control module or BCM stores the odometer reading. The odometer reading is not lost when the battery is disconnected.