Circuit/System Description
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2015 GMC Yukon XL, 2015 GMC Yukon, 2015 Chevrolet Tahoe, 2015 Chevrolet Suburban, and 2015 Cadillac Escalade ESV. However, it is still accessible from the selected car via links, so may be relevant.
When learning the security code, as well as the challenge and response sequence, the engine control module (ECM) is placed in learn mode. Once the security code and challenge/response are learned, learn mode will be exited when the engine is successfully started.