Circuit Description

When an ignition key is inserted in the ignition switch, the terminals located in the ignition lock cylinder contact the resistor pellet in the key. The body control module (BCM) measures the resistance of the key pellet and then compares the resistance to the one stored in memory. If the BCM has been replaced, the new BCM needs to learn the ignition key code value. The BCM learns the first key code value when the ignition is first turned to ON.