Land Rover Discovery: Occupant Monitoring

There are two types of occupant monitoring:

• In all markets except North American Specification (NAS), vehicles have an occupant detection sensor.
• In NAS markets, vehicles have an occupant classification sensing.

Occupant Detection Sensor

1. Occupant detection sensor

The occupant detection sensor is installed in the cushion of the front passenger seat, between the foam padding and the cover. The sensor consists of a foil contact circuit, embedded in a plastic sheet. Weight on the sensor reduces the resistance of the circuit, which is detected by the Central Junction Box (CJB).

The occupant detection sensor has no interface with the SRS. It only provides an input to the CJB for the seatbelt reminder function.

For additional information, refer to: Seatbelt System (501-20A Seatbelt System, Description and Operation).

Occupant Classification Sensing

1. Occupant Classification Sensor Control Module (OCSCM)
2. Seatbelt tension sensor

In North American Specification (NAS) markets where safety belt use is infrequent, additional technology is used to classify the occupant of the front passenger seat. The occupant classification sensing system provides seat load data to the Restraints Control Module (RCM).

The occupant classification system consists of:

• The OCSCM (Occupant Classification Sensor Control Module), installed under the front passenger seat.
• A pressure pad, installed under the cushion of the front passenger seat, which is connected to the OCSCM.
• A seatbelt tension sensor, integrated into the anchor point of the front passenger seatbelt.

The pressure pad is a silicone filled bladder. Any load on the pressure pad is detected by the OCSCM. The seatbelt tension sensor is a strain gauge which measures the load applied by the seatbelt anchor to the anchor bolt.

The sensor is located in the lower seatbelt anchor point.

CAUTION:

The occupant classification sensor control module, hose and pressure pad form a sealed assembly and must not be disassembled. The assembly can only be replaced as part of the occupant classification sensing service kit. The service kit includes the seat cushion pad, because the assembly is specifically calibrated to the pad, and each pad has a unique calibration.

The OCSCM supplies a reference voltage to the seatbelt tension sensor and, from the return signal, measures the load acting on the seatbelt anchor. The measurement is used to produce a correction factor for the load acting on the pressure pad. The tightness of the seatbelt affects the load acting on the pressure pad, so without the correction factor the OCSCM cannot derive an accurate occupancy status.

The OCSCM translates the load readings into a seat occupancy status and transmits the result to the RCM, on the High Speed (HS) Controller Area Network (CAN) powertrain bus.

The RCM monitors and processes the data from the OCSCM before making an airbag deployment decision. The system is designed to take account of several variables in addition to weight, including: inclination of the vehicle and exact position and structure of the weight on the seat.

This protects against inadvertent airbag deployment, for example, if the seat were occupied by an infant in a booster seat, or an unrestrained but very lightweight adult, in both these cases the airbag would be disabled.

The occupant classification sensing system forms part of a strategy to control passenger airbag deployment depending on the occupancy scenario.

The occupant classification sensing has four possible states:

• Seat Empty: the passenger airbag, passenger side airbag and passenger seatbelt pretensioner operation is disabled; the passenger airbag deactivation warning indicator is not illuminated.
• Occupied Inhibit: when the seat is occupied by a small person, the passenger airbag, passenger side airbag and passenger seatbelt pretensioner operation is disabled; the passenger airbag deactivation warning indicator is illuminated.
• Occupied Allow: when the seat is occupied by a large person; the passenger airbag and passenger side airbag operation is enabled, the passenger airbag deactivation warning indicator is not illuminated.

  Passenger seatbelt pretensioner operation status depends on the seatbelt buckle status:

• Active for buckled.
• Inactive for unbuckled.

• Error: if a system fault is detected; the passenger airbag is enabled to deploy at 'stage-1' only, refer to airbag Dual Stage Inflators below.

  Passenger-side airbag operation is also enabled; the passenger airbag deactivation indicator is not illuminated. Passenger seatbelt and pretensioner operation status depends on the seatbelt buckle status:

• Active for buckled.
• Inactive for unbuckled.

Supplemental Restraint System - Component LocationPassenger Airbag Deactivation Indicator

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