Circuit/System Description

The impact sensors are equipped on vehicles to supplement the Supplemental Inflatable Restraint (SIR) System performance. The impact sensors are electronic and are not part of the deployment loops, but instead provide inputs to the Inflatable Restraint Sensing and Diagnostic Module. The impact sensors can assist in determining the severity of some frontal and side collisions. The Inflatable Restraint Sensing and Diagnostic Module uses the input from the impact sensors to assist in determining the severity of a collision further supporting air bag deployment. If the Inflatable Restraint Sensing and Diagnostic Module determines a deployment is warranted, the Inflatable Restraint Sensing and Diagnostic Module will cause current to flow through the deployment loops deploying the appropriate air bags. The Front impact sensor and side impact sensors utilize a bidirectional 2-wire circuit. The sensors modulate current on the interface to send identification, state of health, and deployment commands to the inflatable restraint sensing and diagnostic module. The Inflatable Restraint Sensing and Diagnostic Module serves as a power source and a ground for the sensors. When the ignition is turned ON and input power from the Inflatable Restraint Sensing and Diagnostic Module is first detected, the sensors respond by performing internal diagnostics and sending an identification to the Inflatable Restraint Sensing and Diagnostic Module. The Inflatable Restraint Sensing and Diagnostic Module considers the identification to be valid if the response time is less than 5 seconds. The sensors continually communicate status messages to the Inflatable Restraint Sensing and Diagnostic Module, which determines if a fault is present in the sensor circuit. When a fault is detected, the Inflatable Restraint Sensing and Diagnostic Module may reset the sensors up to 2 times by removing and reapplying power to it. If the fault is still present, the Inflatable Restraint Sensing and Diagnostic Module will set a DTC.