Design [4 of 4]

Inflatable curtains





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

There are two inflatable curtains connected to the supplemental restraint system module (SRS). Their connectors are electrically separated from each other.
The inflatable curtains are located in the roof between the A-post and C-post. They have only one igniter component each. The purpose of the curtain is to protect the head and parts of the upper body in the event of a side-on collision. The supplemental restraint system module (SRS) deploys the inflatable curtain on the side closest to the point of impact.
The inflatable curtain uses 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 curtain, which falls down and covers the door windows and B-post.

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

SRS indication
The supplemental restraint system module (SRS) continuously checks the system. A diagnostic trouble code (DTC) is stored and an SRS indication is made.
SRS indication is accompanied by a text message in the Driver information module (DIM), partly through:
- an SRS warning lamp
- a general warning lamp
- a yellow information lamp.
The lamps light depending on how serious the fault is: Information about which lamp should be lit is transmitted by the supplemental restraint system module (SRS) on the controller area network (CAN).
The SRS warning lamp lights when the ignition is switched on. If no faults are registered by the control module, either internally or from the sensors, wiring or igniters, a signal is transmitted on the controller area network (CAN) to the driver information module (DIM) confirming that the SRS warning lamp can be switched off. If no faults are detected when the ignition is switched on, the lamp will remain lit for a few seconds. The lamp goes out when the system has been checked and is operating without faults.
The control module has an EEPROM memory which retains data about diagnostic trouble codes (DTCs) even when the battery has been disconnected.
The driver information module (DIM) continuously indicates to the supplemental restraint system module (SRS) the function of the SRS warning lamp. If the lamp stops working, the general warning lamp lights up and a message is displayed.

Note! If a diagnostic trouble code (DTC) is stored because the resistance in an SRS ignition cable is too high or too low, it is important that the resistance of the SRS ignition cable is not measured when the collision protection system is connected. Special tools with the same resistance as the collision protection system must be used for fault-tracing.

Passenger airbag indication




The supplemental restraint system module (SRS) transmits signals on the controller area network (CAN) to the central electronic module (CEM) indicating whether the front passenger airbag is activated or not. If the central electronic module (CEM) receives information that the passenger airbag is deactivated, it transmits a signal to the passenger airbag disconnected warning lamp (PAD). The signals are transmitted on a directly connected signal cable. The warning lamp which is in the roof console, lights and remains lit while the passenger seat airbag is disconnected.
Depending on the market, if the switch for activating and deactivating the front passenger airbag is used to deactivate it, the passenger airbag disconnected (PAD) warning lamp lights.
The warning lamp goes out when the airbag is enabled.
If an occupant weight sensor (OWS) is installed (market dependent), the passenger airbag disconnected (PAD) warning lamp lights when the airbag is deactivated. However there is an exception to this (only applies to the S40/V50):
- The passenger airbag warning lamp (PAD) will not light if the passenger airbag is disabled because the occupant weight sensor (OWS) registers that the passenger seat is unoccupied.
The warning lamp goes out when the airbag is enabled.
Reason the passenger airbag warning lamp (PAD) lights could also be:
- communication problems between the supplemental restraint system module (SRS) and central electronic module (CEM)
- faulty function in the on/off switch for the front passenger airbag
- defective occupant weight sensor (OWS) function.

Seat belt buckle




The two front seat belt buckles have Hall sensors and are connected to the SRS module. These connections are electrically separated from each other.
The Hall sensor detects whether the belt is engaged in the seat belt buckle or not and indicates this to the supplemental restraint system module (SRS). The information is used to set the activation level for airbags and seat belt tensioners. If a fault is detected in the seat belt buckles or in their terminals, an adjustment is made for this, depending on the type of fault.
The rear seat belt buckles can be connected (market dependent) to the central electronic module (CEM) which then transmits the status of the seat belt buckles to the SRS (supplemental restraint system) module via the controller area network (CAN). In the event of a fault in the rear seat belt buckles the seat belt tensioners will function as if the seatbelts are fastened (market dependent).

Activating airbags/seat belt tensioners
The collision safety system is extremely advanced. It is able to adapt airbag deployment and the activation of the seat belt tensioners to suit the specific circumstances of a collision. In general it is extremely unlikely that all airbags and seat belt tensioners will be deployed in the same accident. It is possible that only one airbag or seat belt tensioner is deployed. This is determined by the supplemental restraint system module (SRS) based on the forces that occur during the collision.
If the control module deploys the front airbags, both stages will always be activated. By varying the time between the two deployment phases, the inflation of the airbag is more gentle for a low speed collision.

Deployment levels for airbags/seat belt tensioners
The table below shows how the SRS system reacts in the event of a frontal impact.
Level 1= Low speed collision
Level 5 = Severe collision






Side airbag deployment
The table below shows how the SRS system reacts in the event of a side impact.