Part 2

Note! The front passenger airbag switch and occupant weight sensor (OWS) must not both be installed in the vehicle.

Occupant weight sensor (OWS) (USA/CAN only)

The occupant weight sensor (OWS) consists of three interactive components:
- Pressure sensor and silicon pad, installed under the seat cushion in passenger seat front.
- Belt tension sensor, mounted in the seat frame on the outside of the front passenger seat.
- Occupant weight sensor module, installed under the front passenger seat.
The pressure sensor and silicon pad are linked with a hose. The pressure sensor registers the pressure to which the seat cushion, that is, the silicon pad, is exposed. For example, when someone is sitting in the seat.
Information from the belt tension sensor is also used to ensure the good performance of the system. The belt tension sensor informs the occupant weight sensor module what force the belt is tensioned with. This is done because the pressure measured by the pressure sensor can be affected by the passenger fastening the seatbelt tightly. This means that the passenger exerts greater pressure on the seat than during normal seatbelt use. The passenger is then interpreted as being heavier than he or she is.
Using information from both the pressure sensor and belt tension sensor, the occupant weight sensor performs calculations that give Supplemental Restraint System Module (SRS) the following information:
- Passenger seat empty - airbag passenger front off.
- Passenger seat child - airbag passenger front off.
- Passenger seat big - airbag passenger front on.
The occupant weight sensor (OWS) transmits continuous signals on the internal controller area network (CAN), which the supplemental restraint system module (SRS) and occupant weight sensor (OWS) are connected to. If the occupant weight sensor (OWS) does not function correctly the supplemental restraint system module (SRS) will:
- disable the front passenger airbag
- light the passenger airbag warning lamp (PAD) in the roof console
- light the SRS (supplemental restraint system) warning lamp and display the alert message in the driver information module (DIM).
If a fault occurs in any of the components the following should be noted:
- The pressure sensor and occupant weight sensor module must be replaced at the same time
- The belt tension sensor is replaced separately.

Note! The on/off switch for the front passenger airbag and occupant weight sensor (OWS) must not be installed in the vehicle together.

Front airbags

Warning! Never use an ohmmeter or similar tool to test airbags, inflatable curtains, adaptive belt force limiters, adaptive steering column or belt tensioners. Disconnect airbags, inflatable curtains, adaptive seat belt limiters, adaptive steering column or belt tensioners before testing them. Failure to do so may result in accidental deployment, which in turn could result in serious injury or death.

The airbags at the front of the vehicle are:
- driver airbag, 2 stage deployment
- front passenger airbag, 2 or 3-stage deployment.
The driver's airbag is located in the steering wheel. The passenger airbag is located above the glove compartment in the dashboard.
Each airbag stage has a separate igniter component. These are electrically separated from each other. This means that the different ignition components have their own separate power supply and grounding points from the control module.
During airbag deployment, electrical signals are transmitted from the supplemental restraint system module (SRS) to the relevant airbag stage.
Stage 1
Stage 1 of the driver's airbag is pyrotechnic. In the event of deployment, the charge combusts and the gas which develops is blown into the airbag.
Stage 1 on the passenger airbag consists of a pyrotechnic component in combination with a reservoir which stores a gas. In the event of deployment, the pyrotechnic charge combusts and mixes with the stored gas. The gas mixture inflates the airbag.
Stage 2
Stage 2 of the driver's and passenger airbags is pyrotechnical. In the event of deployment, the charge combusts and the gas which develops is blown into the airbag.
The time lapse of the airbag's 2-stage deployment depends on the type of collision and seat belt usage. Both stages are always deployed. In the event of a minor collision, there is a long delay between stages 1 and 2, generating a soft airbag. In the event of a severe collision, there is a short delay between stages 1 and 2, generating a harder airbag.
Stage 3 (front passenger airbag only - USA/CAN)
Stage 3 of the front passenger airbag is pyrotechnical. Upon deployment, a valve opens on the airbag.
Using information from the seat position sensor, belt buckle sensor and impact sensor, the control module can adjust the inflation volume of the airbag to the severity of the collision. This is done by ventilating the airbag.

Adaptive steering column (USA/CAN only)

Warning! Never use an ohmmeter or similar tool to test airbags, inflatable curtains adaptive belt force limiters, adaptive steering column or belt tensioners. Disconnect airbags, inflatable curtains, adaptive belt force limiters, adaptive steering column or belt tensioners before testing them. Failure to do so may result in accidental deployment, which in turn could result in serious injury or death.

When the impact protection in the adaptive steering column is deployed, a pin is triggered that makes the steering column more deformable. In the event of a severe impact, it will possible to press the steering wheel toward the dashboard to a greater degree than if the steering column were rigid.
Steering is not affected by the deployment of the pin. The pin is deployed by a pyrotechnical charge and is located in the center of the steering column. The impact protection system in the adaptive steering column only deploys if the driver is wearing the seat belt and when the airbag is deployed. The entire steering column must be replaced if the impact protection system in the adaptive steering column has deployed.

Side impact air bags

The two front seat belt buckles have Hall sensors and are connected to the SRS module. These connections are electrically separated from each other.
In some markets, each rear belt buckle also contains a Hall sensor, which is also connected to the supplemental restraint system module (SRS). These connections are electrically separated from each other.
The Hall sensor detects whether the belt is fastened in the buckle and sends information on belt detection to the Supplemental restraint system module (SRS). Information on belt detection is used to adapt the deployment level of airbags and belt tensioners. If a fault is detected in the belt buckles or their connections, there could also be adaption to this depending on the type of fault.

Belt tensioners

USA/CAN

Other

Warning! Never use an ohmmeter or similar tool to test airbags, inflatable curtains, adaptive belt force limiters, adaptive steering column or belt tensioners. Disconnect airbags, inflatable curtains, adaptive seat belt limiters, adaptive steering column or belt tensioners before testing them. Failure to do so may result in accidental deployment, which in turn could result in serious injury or death.

Depending on the market, the vehicle may have up to six belt tensioners. Five of these are located at shoulder height - one for each belt retractor - two in the front (1 and 2) and three in the backseat (3, 4 and 5).
In some markets, there is also a belt tensioner (6) located in the belt anchorage waist-high at the driver's seat.
The belt tension contains a pyrotechnical charge that tensions the belt upon deployment.
The belt tensioner tensions the seat belt to reduce the forward movement of the body. This also reduces the forces on the chest from the airbag and seat belt.
The supplemental restraint system module (SRS) determines whether to deploy the respective belt tensioner based on whether the seat belt is in use. The belt tensioner will not be deployed if the seat belt is not fastened. If the seat belts are fastened and seat belt indication in the front seat belt buckles does not function, the belt tensioners will be deployed anyway. Rear belt tensioner deployment is market dependent.
The belt tensioner consists of a pyrotechnical charge and a cylinder with a piston. The piston is connected to a steel cable which is secured to the seat belt retractor. When the control module deploys the belt tensioner, the piston is forced downward by the expanding gas. The piston pulls in the steel cable which retracts the belt.
For USA/CAN: the adaptive belt force limiter, belt retractor, belt retractor sensor and belt tensioner are mounted in a unit. If there is a fault in any of these components, the entire unit must be replaced.

Adaptive seatbelt force limiter (only XC60 or USA/CAN)

Warning! Never use an ohmmeter or similar tool to test airbags, inflatable curtains adaptive belt force limiters, adaptive steering column or belt tensioners. Disconnect airbags, inflatable curtains, adaptive belt force limiters, adaptive steering column or belt tensioners before testing them. Failure to do so may result in accidental deployment, which in turn could result in serious injury or death.

The adaptive belt force limiters improve the function of the seat belt in the event of a head-on collision that triggers airbag deployment. There are two adaptive belt force limiters in the vehicle. These are integrated in the belt retractors of the driver and front passenger seat and sit at shoulder height. The two adaptive belt force limiters are electrically separated from each other. They have a pyrotechnical charge that upon deployment reduces belt force to reduce the forces against the chest.
The adaptive belt force limiter, belt retractor, belt retractor sensor and belt tensioner are mounted in a unit. If there is a fault in any of these components, the entire unit must be replaced.

Belt retractor sensor

Note! Belt retractor sensors are available for XC60 on all markets. For S80 (07-)/S80L/V70 (08-)/XC70 (08-) there are belt retractor sensors only for USA/CDN.

The belt retractor sensor monitors the status of belt extension.
The belt retractor sensor sends information on the status of belt extension to the control module in real time. The control module then analyzes the obtained values and uses the results so that the belt force limiter can optimize belt force for the person occupying the seat.
There are two belt retractor sensors in the vehicle - one on the driver's side belt retractor and one on the front passenger side belt retractor.
Data is transmitted on the same cable used for power supply. There is a signal/power supply cable for each belt retractor sensor as well as a ground cable.
The adaptive belt force limiter, belt retractor, belt retractor sensor and belt tensioner are mounted in a unit. If there is a fault in any of these components, the entire unit must be replaced.