Circuit/System Description

WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.

The inflatable restraint discriminating sensors utilizes a unidirectional 2-wire circuit. The 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 each of the sensors. When the ignition is turned ON and input power from the SDM is first detected, each 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 sensors continually communicates status messages to the SDM, which determines if a fault is present in the sensor or circuit. When a fault is detected, the SDM may reset the appropriate sensor up to 2 times by removing and reapplying power to it. If the fault is still present, the SDM will set a DTC.