Driver Passenger Applicable Pretensioner Driver airbag Passenger airbag Fastened - -
Fired at pretensioner
threshold Fired at belt fastened
threshold - Unfastened - - Not fired
Fired at belt unfastened
threshold - - Fastened Occupied allow
Fired at pretensioner
threshold -
Fired at belt fastened
threshold - Fastened
Unoccupied inhibit/empty Fired at pretensioner
threshold - Not fired - Unfastened Occupied allow Not fired -
Fired at belt unfastened
threshold Unfastened
Unoccupied inhibit/empty Not fired - Not fired The battery disconnect unit is fired:
At driver and passenger airbag belt fastened threshold in a frontal impact
At the driver and passenger side impact threshold in a side impact
At the rear impact threshold in a rear impact.
Crash Signal
When the RCM outputs any of the fire signals it also outputs a crash signal to the RJB and the ECM (engine control module) on the high speed CAN. The crash signal is also hardwired to the ECM and the RJB. The instrument cluster picks up the crash signal from the high speed CAN and gateways it to the LCM (lighting control module). On receipt of the crash signal, the RJB goes into a crash mode and the ECM cuts the power supply to the fuel pump relay. In the crash mode, the RJB: Activates all of the unlock signals of the vehicle locking system, even if the vehicle is already unlocked.
Ignores all locking/superlocking inputs until it receives an unlock input, when it returns the locking system to normal
operation.
Activates the interior lamps. The interior lamps remain on permanently until they are manually switched off at the lamp
unit, or the RJB crash mode is switched off and they return to normal operation. Disables the rear window child lock input until the crash mode is switched off.
Sends a crash message to the LCM, to activate the hazard flashers. The hazard flashers remain on until cancelled by the hazard warning switch or the crash mode is switched off.
The RJB crash mode is switched off by a valid locking and unlocking cycle of the locking system.
Restraints Control Module Component Description
The RCM is installed on the top of the transmission tunnel, in line with the B pillars, and controls operation of the SRS (supplemental restraint system). The main functions of the RCM include:
Crash detection and recording
airbag and pre-tensioner firing
Self-test and system monitoring, with status indication via the airbag warning lamp and non-volatile storage of fault
information.
The RCM determines which elements of the SRS are to be deployed by using two internal areas:
and the safety belt buckle sensor. Based on this data, the RCM decides which level of airbag module deployment is required and forwards the information to the second area, the deployment handler.
The deployment handler evaluates the status of the seat track position sensor and safety belt buckle sensors before a decision
is made about which restraints should finally be deployed.
Data from the side crash sensors is used by the RCM in conjunction with acceleration data from the RCM internal accelerometer to make a deployment decision. The RCM processes the acceleration data and subject to an impact being of high enough severity, decides whether the side airbag module should be deployed.
On board testing of the airbag modules, front safety belt pretensioner firing circuits, warning indicator circuits and module
status (the crash and side impact sensors perform basic self-tests) is performed by the RCM together with the storing of fault codes.
The RCM drives the SRS indicator on the instrument pack via a CAN signal. If the warning lamp fails, a fault code is recorded and a warning tone is sounded in place of the lamp if a further fault occurs. It also provides a temporary back-up power supply
to operate the airbag modules in the event that in crash conditions, the battery supply is lost. In the event of a crash, it
records certain data which can be accessed via the diagnostic connector.
A safing sensor in the RCM provides confirmation of an impact to verify if airbag and pretensioner activation is necessary. A roll-over sensor monitors the lateral attitude of the vehicle. Various firing strategies are employed by the RCM to ensure that during an accident only the appropriate airbags and pretensioners are fired. The firing strategy used also depends on the
inputs from the safety belt switches and the occupant monitoring system.
An energy reserve in the RCM ensures there is always a minimum of 150 milliseconds of stored energy available if the power supply from the ignition switch is disrupted during a crash. The stored energy is sufficient to produce firing signals for the
driver airbag, the passenger airbag and the safety belt pretensioners.
When the ignition is switched on, the RCM performs a self-test and then performs cyclical monitoring of the system. If a fault is detected the RCM stores a related fault code and illuminates the airbag warning indicator. The faults can be retrieved by the recommended Jaguar diagnostic tool over the CAN bus. If a fault that could cause a false fire signal is detected, the RCM disables the respective firing circuit, and keeps it disabled during a crash event.
Clock Spring
The clockspring is installed on the steering column to provide the electrical interface between the fixed wiring harness of the
steering column and the components that rotate with the steering wheel, i.e. the driver airbag, the horn and the steering
wheel switch packs.
The clockspring consists of a plastic cassette which incorporates an outer cover fixed to the steering column and an inner rotor
which turns with the steering wheel. Four securing lugs attach the cover to the multifunction switch on the steering column.
The rotor is keyed to the steering wheel by a drive peg. A lug on the underside of the rotor operates the self-cancelling feature
of the turn signal indicator switch. A ribbon lead, threaded on rollers in the rotor, links two connectors on the cover to two
connectors on the rotor. Link leads for the driver airbag are installed in one of the connectors on the rotor.
To prevent damage to the ribbon lead, both the steering and the clockspring must be centralized when removing and installing
the clockspring or the steering wheel. The clockspring is centralized when the drive peg is at six o'clock and 50 - 100% of a
yellow wheel is visible in the viewing window.
Replacement clocksprings are fitted with a stopper, which locks the cover to the rotor, in the central position. The stopper must
be broken off when the replacement clockspring is installed.
