Impact Sensor: Description and Operation

The Inflatable Restraint Side Impact Sensors (SIS)
The Inflatable Restraint Side Impact Sensors (SIS) are pressure-sensitive devices used in the detection of side impact collisions. The Inflatable Restraint Side Impact Sensor (LH) is located in the LH front door. The Inflatable Restraint Side Impact Sensor (RH) is located in the RH front door. The Inflatable Restraint Side Impact Sensors are used to perform the following functions:
^ Side Impact Crash Detection - Each SIS monitors vehicle velocity changes to detect side impact crashes that are severe enough to warrant deployment.
^ Side Air Bag System Status Communication - The Inflatable Restraint Sensing and Diagnostic and Seat Belt Pretensioner Module (SDM) monitors a diagnostic line from each SIS. Both SISs communicate the status of the side impact air bag system to the SDM over these diagnostic lines.

The SIS connects to the air bag wiring harness using a 2-way connector.
The SIS receives power via the SDM whenever the ignition switch is in the ON or START positions.

The SIR sensor replacement policy requires replacing the Inflatable Restraint Side Impact Sensors in the area of accident damage. The area of accident damage is defined as the position of the vehicle which is crushed, bent, or damaged due to a collision. For example, a moderate collision where the front of the vehicle impacts a tree. If the vehicle has a SIR sensor mounted forward of the radiator, it must be replaced.
^ Replace the sensor whether or not the relevant Side Air Bag has deployed.
^ Replace the sensor even if it appears to be undamaged.

Sensor damage which is not visible, such as slight bending of the mounting bracket or cuts in the wire insulation, can cause improper operation of the SIR sensing system. Do not try to determine whether the sensor is undamaged, replace the sensor. Also, if you follow a Diagnostic Trouble Code (DTC) table and a malfunctioning sensor is indicated, replace the sensor.