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Side impact sensor

Side impact sensor


The purpose of the side impact sensor is to identify a side collision and then send a signal to the SRS control module, which will respond to the signal by activating the side airbag on the side of the car in question.

Two leads from the SRS control module are connected to the side impact sensor. They supply current to the sensor and are also used for communication between the side impact sensor and the control module.

The side impact sensor is specific to the door and the car on which it is fitted. There are four different sensors.


• Driver, 5D

• Passenger, 5D

• Driver, 3D

• Passenger, 3D


The side impact sensor on the driver's side is connected to pins 41 and 42 of the control module. The sensor on the passenger's side is connected to pins 43 and 44 of the control module.

In the side impact sensor is a pressure sensor which reacts to changes in the air pressure inside the door. A microprocesor in the side impact sensor processes the pressure information and determines whether it matches the limiting values that are defined for a collision.



The side impact sensor communicates by modulating the supply of current from the SRS control module. The changes are then registered by the microprocessor in the control module.

The communication may consist of the following messages:


a. Identification of driver side or passenger side.

b. Status of side impact sensor, whether defective or OK.

c. Activation messages for a side airbag.


The SRS control module starts the power supply to the side impact sensor when the ignition switch is turned to the ON position, whereupon the sensor spontaneously reports its status. From then on the status message is sent at regular intervals in normal operation. If the SRS control module is configured for a side impact airbag but does not make contact with any of the side impact sensors within 10–20 seconds a diagnostic trouble code is generated for the affected sensor. The control module goes on trying to restore communication with the side impact sensor that caused the trouble.

On the basis of information from the side impact sensor, the SRS control module reaches a decision concerning diagnostic trouble codes related to the side impact sensor.

A command from the side impact sensor to the control module to activate a side airbag must consist of several messages. This obviates the risk of the control module activating the side airbag on account of some electronic malfunction.

A diagnostic trouble code is generated when a side airbag has been activated, and further communication with the side impact sensor will be ignored by the control module.