Here is the tutorial on programming smart key for Cadillac CT6 2016 under all keys lost situation by using OBDSTAR X300 Pro3 Key Master auto key programmer. Preparation: Two smart keys OBDSTAR X300 Pro3 key programmer Pin Code to car (get pin code by VPC-100 or other calculators) Instruction: Connect OBDSTAR X300 Pro3 key programmer with vehicle Select Vehicles Select Immobilizer Select GM Select GM V30.44 Select Immo/Remote function Select vehicle make: Cadillac Select CT6 Select Immobiliser Select vehicle year: 2016 Select All keys lost Press start button once Put the smart key into the card slot,take other smart key out of the car,press ENTER to continue. The position of card slot is as follows: 1. In the armrests 2.Below the cup holder 3.Near the ashtray 4.Glove compartment Switch igntion off Configuring the system,please wait OBDSTAR Key Master require to enter 4-digit pin code Enter pin code and confirm Verifiy the security code Configuring the system,please wait for about 12 minutes Erease success Press start button once X300 Pro3 prompt whether to program next key? Press ENTER to continue Remove key from card slot and out of car, and change another smart key, put the seconds key into the card slot Press start button once whether to program next key? Press ENTER, turn ignition OFF Press start button for 12 sec Release start button and then press ENTER Press start button to swtich ignition on Switch ignition off Press the brake and press the start button to start the engine Switch ignition off Remove smart key, press LOCK, and then press UNLOCK, press ENTER to continue Test new smart key is working Program success!