L322 Range Rover Restraint Systems: Description (Page 376)
RESTRAINT SYSTEMS
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DESCRIPTION AND OPERATION
Side Impact Sensor
A side impact sensor is installed in each B/C post and connected to the DCU. The use of independent side impact
sensors provides shorter airbag triggering times, through faster detection of lateral acceleration, and improves
detection accuracy.
Each side impact sensor incorporates an accelerometer and a microcontroller powered by a feed from the DCU. The
power feed also provides the interface connection through which the side impact sensor communicates with the DCU
using serial data messages. Lateral acceleration is evaluated by the microcontroller and transmitted to the DCU,
which then makes the decision on whether or not to activate the side and head airbags.
When the ignition is switched on the DCU supplies power to the side impacts sensors, which perform a self test. After
satisfactory self tests the side impact sensors continually output 'sensor active' messages to the DCU. If a fault is
detected the relevant side impact sensor sends a fault message, instead of the sensor active message, to the DCU,
which stores a related fault code in memory and illuminates the SRS warning lamp. Faults can be retrieved by
TestBook/T4 from the DCU via the K bus connection with the instrument pack.
Seat Occupancy Sensor
The seat occupancy sensor is installed in the cushion of the front passenger seat between the foam padding and the
cover. The sensor consists of a foil contact circuit, embedded in a plastic sheet. Weight on the sensor reduces the
resistance of the circuit.