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Side impact sensor

Side impact sensor


The role of the side impact sensor is to identify a side-on collision and then send a message to the SRS control module, which in turn triggers the airbag on the side of impact.

Two leads are connected to the side impact sensor from the SRS control module. These leads are used to supply power and communicate between the side impact sensor and the control module.

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


• Driver, 4D

• Passenger, 4D

• Driver, 5D

• Passenger, 5D


The side impact sensor is connected to the control module as indicated in Control module connections , Airbag (SRS) LHD and Airbag (SRS) RHD .

The side impact sensor contains a pressure sensor that reacts upon relative changes in the air pressure inside the door. A microprocessor in the side impact sensor processes the pressure information and checks that it corresponds to the limit values defined for a collision.


The side impact sensor communicates by modulating the feed supply 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 message, information on faulty or correct side impact sensor.

c. Activation of side airbag.


The SRS control module supplies power to the side impact sensor when the ignition is switched to the ON position, at which time the side impact sensor responds with its status. A status message is then sent at even intervals during normal operation. If the SRS control module is configured for the side airbag, but does not have any contact from the side impact sensor within 10-20 seconds, a DTC is set for the side impact sensor. The control module continues to try to re-establish communication with the side impact sensor that caused the fault.

Based on information from the side impact sensor, the SRS control module determines if DTCs should be set for the side impact sensor.

A command from the side impact sensor to the control module to activate the side airbag must consists of several messages. This avoids the risk of the control module activating the side airbag based on an electrical disturbance.

When a side airbag has been triggered, a DTC is set and the control module ignores any further communication from the side impact sensor.