Circuit/System Description

WARNING: This page does not describe the selected car, but rather 8 other vehicles, including the 2012 GMC Yukon XL, 2012 GMC Yukon, 2012 Chevrolet Tahoe, 2012 Chevrolet Suburban, and 2012 Chevrolet Avalanche. However, it is still accessible from the selected car via links, so may be relevant.

The front impact sensor utilizes a unidirectional 2-wire circuit. The front impact sensor modulates current on the interface to send ID, state of health, and deployment commands to the inflatable restraint sensing and diagnostic module (SDM). The SDM serves as a power source and a ground for the front impact sensor. When the ignition is turned ON and input power from the SDM is first detected, the front impact sensor responds by performing internal diagnostics and sending an ID to the SDM. The SDM considers the ID to be valid if the response time is less than 5 seconds. The front impact sensor continually communicates status messages to the SDM, which determines if a fault is present in the front impact sensor circuit. When a fault is detected, the SDM may reset the front impact sensor up to 2 times by removing and reapplying power to it. If the fault is still present, the SDM will set a DTC.