DESCRIPTION AND OPERATION
RANGE ROVER 4.51
Head Airbags
The SRS DCU registers a side impact via the side impact sensors, which are mounted at
the base of the LH and RH B/C posts. The SRS DCU monitors the condition of the RH
sensor (C0951) and the LH sensor (C0950) on YR and YG wires respectively. Both sensors
are earthed on NB wires. When the SRS DCU registers a side impact above its threshold
level, it will fire the relevant head airbag.
LH Front
The SRS DCU (C0256) provides a firing signal to the LH front head airbag (C1477) on a UY
wire. An earth path is provided by the SRS DCU (C0256) on a Y wire.
RH Front
The SRS DCU (C0256) provides a firing signal to the RH front head airbag (C1478) on a W
wire. An earth path is provided by the SRS DCU (C0256) on a UW wire.
LH Rear
The SRS DCU (C0256) provides a firing signal to the LH rear head airbag (C1474) on a B
wire. An earth path is provided by the SRS DCU (C0256) on a Y wire.
RH Rear
The SRS DCU (C0256) provides a firing signal to the RH rear head airbag (C0948) on a UG
then UR wire. An earth path is provided by the SRS DCU (C0256) on an R then G wire.
Occupancy Detector
The occupancy detector determines if there is a passenger occupying the front seat. If the
front seat passenger is not detected, the front passenger airbag, and front passenger head
airbag deployment is suspended in the event of an impact. All other SRS components will
operate as normal.
The occupancy detector (C0962) is provided an auxiliary ignition feed from fuse 44 of the
passenger compartment fuse box (C0586) on a PG wire, and is earthed on an NB wire. The
occupancy detector (C0962) provides a pulsed voltage signal to the SRS DCU (C0256) on
a WR wire. The signal consists of 7 bits. A signal of '0 00 00 01' informs the SRS DCU the
front passenger seat is unoccupied. A signal of '0 11 11 01' informs the SRS DCU the front
passenger seat is occupied.
Seat Belt Switches
The SRS DCU determines if the front seat belts are being used by monitoring the status of
the seat belt switches. If the seat belt tongue is inserted into the buckle, the switch contacts
close and battery voltage is supplied to the SRS DCU (C0256) on UW (LH) and UP (RH)
wires. If the SRS DCU detects a seat belt is not being used, it will not fire the relevant seat
belt pre-tensioner.
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