Sensors
WARNING: PRIOR TO REMOVAL OF ANY SRS SENSORS AND BEFORE DISCONNECTING ANY SRS SENSOR ELECTRICAL CONNECTORS, THE BATTERY GROUND CABLE SHOULD BE DISCONNECTED AND A PERIOD OF AT LEAST ONE MINUTE ALLOWED TO ELAPSE.
NOTE: The SRS sensors do not contain any serviceable components.
The SRS consists of the following sensors:
Occupancy Sensors
The occupancy sensor locations are identical for both the coupe and convertible, except that since the convertible has no 'B' post, the equivalent sensor is mounted in the rear quarter trim capping. The four sensors are strategically placed to detect the presence and movement of the passenger front seat occupant.
The occupancy sensor system uses ultrasound at an operating frequency of 40 kilohertz to monitor passenger front seat occupancy. The SRS uses four ultrasonic sensors, one at the A-post, one at the 'B' post and two in the roof console. The sensors determine the presence and position of the passenger front seat occupant with respect to the passenger air bag deployment door. The sensors determine air bag module deployment decisions by classifying occupants as either 'in position' or 'out of position'. The sensors are part of a system that is sophisticated enough to be unaffected by body extremities (hands and feet) and respond only to head or body movements.
Obstruction of any sensor for an extended period of time, or repeated key cycles will cause the system to log a 'blocked' code and will illuminate the SRS indicator. Subsequent clearance of the obstruction will reinstate the SRS indicator, but the code will remain logged.
Side Crash Sensors
The side crash sensors are mounted on a bracket attached to the vehicle body, behind each front safety belt retractor. They consist of processing circuits and an accelerometer. They do not make deployment decisions.
Driver Seat Track Position Sensor
The driver seat track position sensor is a 'hall effect' type sensor and is mounted on the underside of the driver seat. It is actuated by a steel blade that is attached to the seat slide. The magnetic field disturbance caused, when the steel blade passes through the sensor, creates an output signal for the RCM. On receipt of this signal, which indicates when the seat is forward of a defined point in its travel, the RCM disables the second stage output of the driver air bag module. Malfunction of the sensor or associated circuits will cause the SRS indicator to illuminate.
Front Seat Passenger Weight Sensing System
NOTE: The front seat passenger weight sensing system does not contain any serviceable components.
Individual components of the front seat passenger weight sensing system are not serviceable. The system must be replaced as a complete unit and due to its sophistication, each replacement system requires calibration, so to avoid the need to provide calibration equipment to each dealer, a pre-calibrated service kit is available. The following components are combined and calibrated during manufacture to form the front seat passenger weight sensing system:
- Passenger seat cushion
- Silicone filled bladder
- Weight sensing control module
- Pressure sensor
The weight sensing control module is mounted under the passenger front seat. The silicone filled bladder is integrated into the seat cushion and the pressure sensor, which is attached to the bladder, is mounted under the seat.
The silicone filled bladder responds to weight changes on the passenger front seat. The pressure sensor responds to these pressure changes and provides an appropriate signal to the weight sensing control module. The weight sensing control module processes the input signal received from the pressure sensor and makes it available to the RCM via the controller area network (CAN). In addition, the weight sensing control module performs self-diagnostic functions on the system, with any malfunctions being notified to the RCM accordingly.
The front seat passenger weight sensing system responds to the occupancy of the passenger front seat in accordance with the following:
- Passenger front seat status 'EMPTY' - Passenger air bag status 'OFF' - PAD indicator 'OFF'
- Passenger front seat status 'OCCUPIED' (small occupant) - Passenger air bag status 'OFF' - PAD indicator 'ON'
- Passenger front seat status 'OCCUPIED' (large occupant) - Passenger air bag status 'ON' - PAD indicator 'OFF'
The SRS via the RCM, monitors and processes data from the front seat passenger weight sensing system and several other sensors before making a deployment decision. Malfunction of the sensing system or associated circuits will cause the SRS indicator to illuminate.
Front Crash Sensor
The front crash sensor is mounted on a bracket which is located on the left-hand side of the radiator upper mounting member. It collects acceleration data from the front of the vehicle and sends it back to the RCM as an analogue signal. It provides the main source of data that enables the RCM to gauge the severity of a frontal impact.
Safety Belt Buckle Sensor
The safety belt buckle sensor is a 'hall effect' type sensor which provides an output signal in response to the magnetic field disturbance caused by the insertion of the safety belt tongue into the buckle. The output signal from the sensor is used by the RCM to determine whether the front seat occupants are correctly restrained. It is used in conjunction with other components of the SRS to ensure that air bag module and safety belt pretensioner deployment only occurs where necessary. It also forms an integral part of the electrical comfort system. Malfunction of the sensor or associated circuits will cause the SRS indicator to illuminate.