The body control module (BCM) stores the theft deterrent passkey code (resistance value) in nonvolatile memory. This key code is stored one time and cannot be changed or relearned. A new service parts BCM does not have a key code stored in memory. When a new BCM is installed in the vehicle, the BCM will learn the first key code it encounters at ignition ON and stores this code in memory. Once the BCM learns a key code, the code cannot be changed. If a BCM from another vehicle is installed, the key code stored in that BCM must be determined and a matching key obtained in order for the theft system to operate properly. Refer to the Replacing Keys procedure in order to determine the stored key code.