2010 JAGUAR XFR Control module

1 Occupant classification system pressure pad (NAS only) 2 Safety belt tension sensor (NAS only) 3 Occupant detection system pad (all, except NAS) 4 Occupant classification system control module (NAS only) 5 RH side impact sensor (pressure sensor) 6 RH rear impact sensor 7 LH rear impact sensor 8 Passenger airbag deactivation LED (light emitting diode) 9 Driver's seat position sensor 10 LH side impact sensor (pressure sensor) 11 Instrument cluster 12 LH front impact sensor 13 RH front impact sensor

Published: 30-May-2012
Supplemental Restraint System - Air Bag and Safety Belt Pretensioner
Supplemental Restraint System (SRS) - Overview
Description and Operation

OVERVIEW


WARNING: All pyrotechnic devices are dangerous. Before performing any procedures on any pyrotechnic device, read all
information contained within the Standard Workshop Practices section of this manual.
Refer to: Standard Workshop Practices (100-00 General Information, Description and Operation).
The SRS (supplemental restraint system) provides additional protection for the vehicle occupants in certain impact conditions.
The system is controlled by the RCM (restraints control module), which is mounted beneath the floor console. The system
includes twin stage drivers and front passenger airbags.
The RCM receives inputs from various sensors around the vehicle and determines which, if any, airbags should be deployed.
The SRS features an occupant detection system. The occupant detection system comprises a mat fitted inside the front passenger seat. By monitoring the condition of the mat, the RCM can determine if the front passenger seat is occupied. It uses this information to determine which airbags to deploy in the event of an impact. This information is also used to illuminate the
safety belt instrument cluster warning lamp if the front passenger seat is occupied and the safety belt is not engaged.

North American Specification (NAS) vehicles also feature an occupant classification system. The occupant classification system
comprises a control module, pressure pad and safety belt tension sensor. The system can determine the size and weight of the
front seat passenger. This information is transmitted to the RCM over the high speed CAN (controller area network) bus. The RCM uses this information to help determine which airbags to deploy in the event of an impact.

Published: 26-Jun-2012
Supplemental Restraint System - Air Bag and Safety Belt Pretensioner
Supplemental Restraint System (SRS) - System Operation and Component Description
Description and Operation

Control Diagram

NOTE: A = Hardwired; D = High speed CAN (controller area network) bus



Item Description 1 Battery 2 BJB (battery junction box) 3 RJB (rear junction box) 4 Occupant classification system control module (NAS only) 5 Safety belt tension sensor (NAS only)

6 Occupant classification system pressure pad (NAS only) 7 Passenger airbag deactivation LED (light emitting diode) 8 Instrument cluster 9 Occupant detection system pad (all, except NAS) 10 Driver's seat position sensor 11 Front passenger seat safety belt pretensioner 12 Driver's seat safety belt pretensioner 13 LH (left-hand) front impact sensor 14 RH (right-hand) front impact sensor 15 RH rear impact sensor 16 RH side impact sensor 17 LH rear impact sensor 18 LH side impact sensor 19 RCM (restraints control module)

Item Description 1 Battery 2 BJB 3 RJB 4 Front passenger airbag 5 Clockspring 6 Driver's airbag 7 Front passenger seat safety belt switch 8 Driver's seat safety belt switch 9 LH curtain airbag 10 Driver's seat thorax airbag 11 Front passenger seat thorax airbag 12 RH curtain airbag 13 RCM


System Operation System Operation

In a collision, the sudden deceleration or acceleration is measured by the impact sensors and the accelerometers in the
restraints control module. The restraints control module evaluates the readings to determine the impact point on the vehicle
and whether the deceleration/acceleration readings exceed the limits for firing any of the airbags, pretensioners, and battery
disconnect unit. During a collision, the restraints control module only fires the airbags and pretensioners if the safing function
confirms that the data from the impact sensor(s) indicates an impact limit has been exceeded.
The RCM incorporates the following impact thresholds to cater for different accident scenarios: Front impact, pretensioners
Front impact, driver and passenger airbags stage 1, belt unfastened
Front impact, driver and passenger airbags stage 1, belt fastened
Front impact, driver and passenger airbags stage 2, belt unfastened
Front impact, driver and passenger airbags stage 2, belt fastened
Rear impact
Driver side impact
Passenger side impact.

The front impact thresholds increase in severity from pretensioners to driver and passenger airbag stage 2, belt fastened (refer
to list above).

Firing Strategies

The safety belt pretensioners are fired when the pretensioner impact limit is exceeded. The RCM only fires the pretensioners if the related safety belt is fastened.

The driver and passenger airbags are only fired in a frontal impact. If an impact exceeds a stage 1 limit, but is less than the
corresponding stage 2 limit, only one inflator in each airbag is fired (stage 2 is still fired for disposal after a delay of 100ms).
If an impact exceeds the stage 2 limit, the two inflators in each airbag are fired simultaneously.

The passenger airbag is disabled unless the front passenger seat is occupied by a large person (NAS only), or the passenger
airbag deactivation switch is on (all except NAS & AUS).

The stage 2 inflator of the driver airbag is disabled if the driver seat is forward of the switching point of the seat position
sensor.

If there is a fault with a safety belt buckle sensor, the RCM assumes the related safety belt is fastened for the pretensioner firing strategy and unfastened for the driver and passenger airbag firing strategies. If there is a fault with the occupant
classification sensor, the RCM disables the passenger airbag. If there is a fault with the passenger airbag deactivation switch, the RCM disables the passenger airbag.
If a side impact limit is exceeded, the RCM fires the side airbag and the side head airbag on that side of the vehicle. If the side impact limit on the front passenger side of the vehicle is exceeded, the RCM also evaluates the input from the occupant classification sensor, and fires the side airbag only if the front passenger seat is occupied by a large person (NAS only).

If multiple impacts occur during a crash event, after responding to the primary impact the RCM will output the appropriate fire signals in response to any further impacts if unfired units are available.

Front and Rear Impact Firing Strategy (All Except NAS)
Safety Belt Status Strategy 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 Fired at pretensioner threshold - Fired at belt fastened threshold - Unfastened Not fired - Fired at belt unfastened threshold www.JagDocs.com

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:

occupant position and the crash severity. To reduce the risk of an airbag module induced injury to a driver that is positioned
close to the steering wheel, the airbag module deploys radially. It has a non-azide propellant that reduces particulates and
effluents. It consists of a two stage inflator with separate chambers for the two inflation stages, each being independently
activated by the RCM. It has two electrical connectors that are color coded and mechanically keyed to the respective connector on the inflator.

Passenger Airbag Module



The passenger airbag module is controlled by the RCM which chooses between single or dual stage deployment, depending on the occupant status and the crash severity. It consists of a two stage inflator with two airbag electrical connectors to
accommodate the two stage inflation.

The heated gas inflator consists of a high-pressure mix of clean air and hydrogen gas, triggered by two separate ignition
squibs. It produces a controlled generation of clean gas to rapidly fill the airbag. It is classified as a stored flammable gas
(not as an explosive) and as such, has less restrictive storage and transportation requirements. It produces a very clean burn
and almost no particulates and is almost free of any toxins, making disposal or recycling much easier. Drivers Airbag Module

provides the interface connection through which the side impact sensor communicates with the RCM using serial data messages. Acceleration is evaluated by the microchip and transmitted to the restraints control module, which then makes the
decision on whether or not to activate the airbags and pretensioners.

When the ignition is switched on, the RCM supplies power to the impact sensors, which perform a self-test. After satisfactory self tests the impact sensors continually output 'digital acceleration' messages to the restraints control module. If a fault is
detected the relevant impact sensor sends a fault message, instead of the digital acceleration message, to the restraints
control module. The RCM then stores a related fault code and illuminates the airbag warning indicator. Faults can be retrieved by the Jaguar approved diagnostic system from the RCM via the high speed CAN bus connection. www.JagDocs.com