Units are set to factory base programming from the previous truck.  Replacement of the Ecm unit must be programmed on the truck properly before installations to avoid any damage to the Ecm.  Make sure proper information was provided to get you the right Ecm for your Application. Cummins Ecm must provide Part # Engine Serial Number and CPL# to avoid damage to Ecm. Caterpillar Engine Ecm must provide Engine Model and Engine Serial number to avoid damage. Detroit Ecm must provide Engine Serial Number Engine Model Number to avoid Damage. International Engine must provide original unit or must do 100% on truck for proper functions and avoid damage to Ecm.  Damage to Ecm due to lack of programming will void warranty and will be non-refundable to sellers discretion.  Some units may have a higher or lower horsepower rating please contact us if you would like to get one to your specs or upgrade.  Every  replacement unit is not guaranteed plug ‘n play. For Plug ‘N Play unit must be a repair service *special case may vary or if customer sends in original to transfer data if *ecm software is validated.