Range Rover Restraint Systems: System Description and Operation
RESTRAINT SYSTEMS
DESCRIPTION AND OPERATION
75-21
Front and Rear Impact Firing Strategy (NAS Only)
The battery disconnect unit is fired:
l
At driver and passenger airbag limit 2 in a frontal impact
l
At the battery disconnect unit limit in a side impact
l
At the rear impact limit in a rear impact.
If one of the side impact limits is exceeded the DCU fires the side airbag and the head airbag(s) on that side of the
vehicle. If the side impact limit on the front passenger side of the vehicle is exceeded, the DCU also evaluates the
input from the seat occupancy module, and fires only the head airbag(s) if the front passenger seat is unoccupied.
In a roll-over, the airbags, pretensioners and battery disconnect unit are only fired if a related impact limit is exceeded.
If multiple impacts occur during a crash event, after responding to the primary impact the DCU will output fire signals
in response to secondary and further impacts if unfired units are available.
Crash Signal
When the DCU outputs any of the fire signals it also outputs a crash signal to the Body Control Unit (BCU) and the
ECM. On receipt of the crash signal, the BCU goes into a crash mode and the ECM cuts the power supply to the fuel
pump relay. In the crash mode, the BCU:
l
Activates all of the unlock signals of the vehicle locking system, even if the vehicle is already unlocked
l
Ignores all locking/superlocking inputs until it receives an unlock input, when it returns the locking system to
normal operation
l
Activates the interior lamps. The interior lamps remain on permanently until they are manually switched off at the
lamp unit, or the BCU crash mode is switched off and they return to normal operation
l
Disables the rear window child lock input until the crash mode is switched off
l
Sends a crash message to the Light Check Module (LCM), via the K bus, instrument pack and I bus, to activate
the hazard warning lamps. The hazard warning lamps remain on until cancelled by the hazard warning switch or
the crash mode is switched off.
The BCU crash mode is switched off by a valid locking and unlocking cycle of the locking system.
Seat Belt Status
Passenger
Seat Status
Strategy
Driver
Passenger
Applicable
Pretensioner
Driver Airbag
Passenger
Airbag
Fastened
–
–
Fired at
pretensioner or
rear impact limit
Fired at limit 2 or
above
–
Unfastened
–
–
Not fired
Fired at limit 1 or
above
–
–
Fastened
Occupied
Fired at
pretensioner or
rear impact limit
–
Fired at limit 2 or
above
Unoccupied
Fired
at
pretensioner or
rear impact limit
–
Not fired
–
Unfastened
Occupied
Not fired
–
Fired at limit 1 or
above
Unoccupied
Not
fired
–
Not fired
