The Garmin eLog™ adapter reads the vehicle mileage directly from the Electronic Control Module (ECM) on the vehicle. Occasionally, variations in the vehicle due to repairs, upgrades, or modifications can cause differences between the instrument cluster and the ECM.

The following items are possible causes of variation.

• The circumference of the tires was changed.

• There are differences between the types of sensors used in the engine ECM and instrument cluster.

• The engine ECM was reprogrammed or replaced.

• The instrument cluster was reprogrammed or replaced.

• Possible firmware defects exist in the instrument cluster or the engine ECM.

• The vehicle manufacturer or supplier accumulated distance while testing vehicle components.