Supplemental Restraint System Control Module (SRS) [2008-2016]: Function
CHECKING THE SRS SYSTEM
When the ignition is switched to position II or III, CAN communication is checked, there is a status check of the internal supplemental restraint system (SRS) functions (4/9) and a status check of all directly connected components, such as:
- driver airbag (8/123)
- passenger airbag (8/124)
- belt tensioners (8/33, 8/34, 8/55 8/56 and 8/62)
- belt tensioner, waist (8/92) (certain markets only)
- side impact sensors (7/108, 7/109, 7/115 and 7/116)
- side impact sensor (pressure sensor) (7/208 and 7/209) (only XC60 or USA/CDN)
- inflatable curtains (8/66 and 8/67)
- SIPS bags (8/51 and 8/52)
- front impact sensor (7/178 and 7/179) (not XC60)
- front seat belt buckles (3/93 and 3/94)
- rear belt buckles (3/217, 3/218 and 3/219) (certain markets only)
- adaptive steering column (8/99) (only USA/CDN)
- seat position sensor (3/255 and 3/256) (only USA/CDN)
- adaptive seatbelt force limiter (8/128 and 8/129) (only XC60 or USA/CDN)
- seatbelt retractor sensor (7/194 and 7/195) (only XC60 or USA/CDN)
- switch airbag passenger front (3/157) (not USA/CDN)
- occupant weight sensor (OWS) (7/93) (only USA/CDN)
In addition to these directly connected components, communication with Closing Velocity Module (CVM) (4/125) (only XC60) is also checked.
The supplemental restraint system module (SRS) transmits information via the controller area network (CAN) to the driver information module (DIM) (5/1) indicating that this test is in progress. The central electronic module (CEM) (4/56) also transmits the parameter values during the status check.
The driver information module (DIM) then lights the SRS warning lamp. The SRS warning lamp is lit while the supplemental restraint system (SRS) is being checked. When the supplemental restraint system (SRS) has been tested and no faults have been detected, the SRS warning lamp goes out.
If a fault is detected during the check it will be indicated in one of the following ways, depending on how serious it is:
- the SRS warning lamp remains lit and a warning text is displayed in the driver information module (DIM)
- the general red warning lamp lights and a warning text is displayed in the driver information module (DIM)
- information light is lit and any text message is shown on the Driver information module (DIM) (2008-).
The driver information module (DIM) continuously sends a signal via the CAN to the Supplemental restraint system module (SRS) with information about if the SRS-warning light is working or not. If the SRS-warning light stops working, the general red warning light is activated. If the CAN-communication between the Supplemental restraint system module (SRS) and Driver information module (DIM) stops, the SRS warning light is activated and an associated warning text is shown on the display in the Driver information module (DIM). If the malfunctions disappear and the Driver information module (DIM) can send information again to the Supplemental restraint system module (SRS), and the status of the SRS-warning light is OK, the warning lights will return to normal function.
HEAD-ON COLLISION (NOT USA/CDN)
In the event of a head-on collision, a function called multi-point detection is used. This means that the collision pulse is registered at several points. This function is integrated in the supplemental restraint system module (SRS) (4/9). When the collision pulse is sufficiently large, a deployment signal (current pulse) is sent to:
- front airbags (8/123 and 8/124) and/or
- belt tensioners (8/33, 8/34, 8/55, 8/56, 8/62 and 8/92) and, if necessary, to
- the inflatable curtains (8/66 and 8/67).
The front collision sensors (7/178 and 7/179) (not XC60)are also included in the multi-point sensing in the control module. They register the collision pulse and send acceleration data to the control module.
Airbags driver and passenger front are activated. Belt tensioners are activated.
Inflatable curtains on driver's side are activated. (2008-).
The passenger airbag will not be activated if it is deactivated with the switch (3/157).
When impact protection has been deployed, the supplemental restraint system module (SRS) sends a collision signal to the central electronic module (CEM) (4/56) and phone module (PHM) (16/60) via a directly connected cable. A collision status signal is also sent to the central electronic module (CEM) and phone module (PHM) on CAN. These two control modules ensure that:
- switch off the fuel pump (FP)
- switch off the windshield wipers when the car is stationary
- turn off defrosting of windows and rearview mirrors if the vehicle is stationary
- light the interior lighting
- light the flashing hazard lights
- unlock the central locking system
- send an automatic alarm to CSC (Customer Service Center) when an accident has occurred - provided the vehicle is equipped with Volvo On Call (Plus).
- turn off the fuel engine heater
Supplemental Restraint System module (SRS) receives continuous information from Closing Velocity Module (CVM) (4/125) (only XC60). With laser Closing Velocity Module (CVM) detects if the vehicle is about to collide with an object in front. Information is used by Supplemental Restraint System Module (SRS) to get an early indication that the vehicle is about to collide, which helps to decide what type of action is needed.
Vehicles with Closing Velocity Module (CVM) have no front impact sensor.
FRONT-END COLLISION (ONLY USA/CDN)
In the event of a head-on collision, a function called multi-point detection is used. This means that the collision pulse is registered at several points. This function is integrated in the supplemental restraint system module (SRS) (4/9). When the collision pulse is sufficiently large, a deployment signal (current pulse) is sent to:
- front airbags (8/123 and 8/124) and/or
- belt tensioners (8/33, 8/34, 8/55, 8/56, and 8/62) and, if certain conditions are met, also to
- the inflatable curtains (8/66 and 8/67).
The front impact sensors (7/178 and 7/179) (not XC60)are also part of the control module's multi-point detection. They register the collision pulse and send acceleration data to the control module. The driver and front passenger airbags are deployed. The belt tensioners are deployed. The inflatable curtains may be deployed. In a head-on collision in which the front airbags and front belt tensioners have been deployed, the adaptive belt force limitation function (see below) could also be activated. If the driver's airbag is deployed and the driver's seat belt is fastened, the control module sends a deployment signal (current pulse) to the adaptive steering column (8/99). The front passenger airbag will not be deployed if it has been disabled via the occupant weight sensor (OWS) (7/93).
A impact signal is sent on a directly connected cable from the Supplemental restraint system module (SRS) to the Central electronic module (CEM) (4/56) when the impact protection has been activated.
An impact status signal is also transmitted to the Central electronic module (CEM) on the CAN. The Central electronic module (CEM) ensures that:
- switch off the fuel pump (FP)
- switch off the windshield wipers when the car is stationary
- turn off defrosting of windows and rearview mirrors if the vehicle is stationary
- light the interior lighting
- light the flashing hazard lights
- unlock the central locking system
- turn off the fuel engine heater
Supplemental Restraint System module (SRS) receives continuous information from Closing Velocity Module (CVM) (4/125) (only XC60). With laser Closing Velocity Module (CVM) detects if the vehicle is about to collide with an object in front. Information is used by Supplemental Restraint System Module (SRS) to get an early indication that the vehicle is about to collide, which helps to decide what type of action is needed.
Vehicles with Closing Velocity Module (CVM) have no front impact sensor.
SIDE COLLISION (NOT USA/CDN)
In event of a side-on collision, the side impact sensors (7/108, 7/109, 7/115, 7/116, 7/208 and 7/209), in the left and right sides of the vehicle, evaluate the stresses in the impact pulse.
Side impact sensors (pressure sensors) right and left front door (7/208, 7/209) only on XC60.
If the impact pulse is sufficiently strong, the level of the acceleration signal from the side impact sensor exceeds the calculated activation level for the impact protection in the Supplemental restraint system module (SRS) (4/9).
The control module must also receive another acceleration signal, either from the acceleration sensors in the control module or another side impact sensor.
If the signal from the impact sensor/control module meets the conditions for deploying the following components, the control module sends a current pulse to the relevant components:
- SIPS bags (8/51 and 8/52)
- inflatable curtains (8/66 and 8/67) and
- belt tensioners (8/33 and 8/34 and on certain markets 8/92 (waist)).
When impact protection has been deployed, the supplemental restraint system module (SRS) also sends a collision signal via a directly connected cable to the central electronic module (CEM) (4/56) and phone module (PHM) (16/60). A collision status signal is also sent to the central electronic module (CEM) and phone module (PHM) on CAN. These two control modules ensure that:
- switch off the fuel pump (FP)
- switch off the windshield wipers when the car is stationary
- turn off defrosting of windows and rearview mirrors if the vehicle is stationary
- light the interior lighting
- light the flashing hazard lights
- unlock the central locking system
- send an automatic alarm to CSC (Customer Service Center) when an accident has occurred - provided the vehicle is equipped with Volvo On Call (Plus).
- turn off the fuel engine heater
SIDE COLLISION (USA/CDN ONLY)
In event of a side-on collision, the side impact sensors (7/108, 7/109, 7/115, 7/116, 7/208 and 7/209), in the left and right sides of the vehicle, evaluate the stresses in the impact pulse.
If the collision pulse is powerful enough, the level of the acceleration signal from the side impact sensors will exceed the calculated activation level for the collision protection system in the supplemental restraint system module (SRS) (4/9).
The control module must also receive another signal, either from the acceleration sensors in the control module or another side impact sensor.
If the signal from the impact sensor/control module meets the conditions for deploying the following components, the control module sends a current pulse to the relevant components:
- SIPS bags (8/51 and 8/52)
- inflatable curtains (8/66 and 8/67) and
- belt tensioners (8/33 and 8/34).
The Supplemental restraint system module (SRS) also transmits an impact signal on a directly connected cable to the Central electronic module (CEM) (4/56) when the impact protection has been activated.
An impact status signal is also transmitted to the Central electronic module (CEM) on the CAN. The Central electronic module (CEM) ensures that:
- switch off the fuel pump (FP)
- switch off the windshield wipers when the car is stationary
- turn off defrosting of windows and rearview mirrors if the vehicle is stationary
- light the interior lighting
- light the flashing hazard lights
- unlock the central locking system
- turn off the fuel engine heater
REAR-END COLLISION
USA/CDN
Other
In the event of a rear-end collision, the supplemental restraint system module (SRS) (4/9) evaluates the force of the collision pulse. If the collision pulse is powerful enough, a deployment signal (current pulse) is sent to the front belt tensioners (8/33 and 8/34) and the front waist belt tensioner (8/92) (certain markets only). The belt tensioners are deployed.
The Supplemental restraint system module (SRS) also transmits an impact signal on a directly connected cable to the Central electronic module (CEM) (4/56) and Phone module (PHM) (16/60) (not USA/CDN) when the impact protection has been activated.
A collision status signal is also sent to the central electronic module (CEM) and phone module (PHM) (not USA/CDN) on CAN. These two control modules make sure that:
- switch off the fuel pump (FP)
- switch off the windshield wipers when the car is stationary
- turn off defrosting of windows and rearview mirrors if the vehicle is stationary
- light the interior lighting
- light the flashing hazard lights
- unlock the central locking system
- send an automatic alarm to CSC (Customer Service Center) when an accident has occurred - provided the vehicle is equipped with Volvo On Call (Plus).
- turn off the fuel engine heater
ROLL-OVER (ONLY XC60)
In case of vehicle roll-over the roll-over sensor senses the vehicle's lateral angle.
Supplemental Restraint System Module (SRS) starts a calculation how high the rotation energy is. If the rotation energy is high enough, the control module will activate the roll-over protection.
All seatbelt tensioners in the vehicle, front (8/33, 8/34), rear (8/55, 8/56, 8/62) and front waist (8/92) (only certain markets), will then be activated. Also inflatable curtains (8/66, 8/67) will be activated.
The Supplemental restraint system module (SRS) also transmits an impact signal on a directly connected cable to the Central electronic module (CEM) (4/56) and Phone module (PHM) (16/60) (not USA/CDN) when the impact protection has been activated.
A collision status signal is also sent to the central electronic module (CEM) and phone module (PHM) (not USA/CDN) on CAN. These two control modules make sure that:
- switch off the fuel pump (FP)
- switch off the windshield wipers when the car is stationary
- turn off defrosting of windows and rearview mirrors if the vehicle is stationary
- light the interior lighting
- light the flashing hazard lights
- unlock the central locking system
- send an automatic alarm to CSC (Customer Service Center) when an accident has occurred - provided the vehicle is equipped with Volvo On Call (Plus)
- turn off the fuel engine heater
FUNCTION FOR ADAPTIVE SEATBELT FORCE LIMITATION (ONLY XC60 OR USA/CDN)
In case of a front-end collision where the front airbags and the front belt tensioners (8/33 and 8/34) have deployed, the function for adaptive belt force limitation can also be triggered. When the front airbags and the front belt tensioners are deployed, the belt retractor sensor (7/194, 7/195) starts to monitor the angle and the speed with which the seat belt is tensioned/tightened. The belt retractor sensor sends information about the seat belt angle and speed to the supplemental restraint system module (SRS) (4/9) in real time. The supplemental restraint system module (SRS) also receives information from the seat position sensor (3/255, 3/256) about the position of the passenger or driver's seat. Then the control module can determine if the person in the vehicle is small or large. With this information, the supplemental restraint system module (SRS) decides if the belt force limiter should be deployed. If the adaptive belt force limiter (8/128, 8/129) is deployed, the supplemental restraint system module (SRS) sends a deployment signal (current pulse) to the adaptive belt force limiter, which reduces the force from the seat belt against the chest.
DEACTIVATING/ACTIVATING AIRBAG PASSENGER FRONT (NOT USA/CDN)
If necessary, the front passenger airbag (8/124) can be disabled. This is done using a switch (3/157) located on the dashboard on the passenger side.
When the switch position is changed from "ON" to "OFF", there is a change to the current levels of the two Hall sensors connected to the switch. The Hall sensors send the changed current levels to the supplemental restraint system module (SRS) (4/9) via directly connected cables. The control module software then disables the front passenger sensor, which means that the airbag will not be deployed in the event of a collision. The supplemental restraint system module (SRS) will also light the passenger airbag warning lamp (PAD) (10/22).
When the switch position changes from "OFF" to "ON", a new current level is sent from the Hall sensors to Supplemental restraint system module (SRS). Then the control module's software activates the airbag, which means that the airbag has full functionality in case of a collision.
Then Supplemental restraint system module (SRS) also turns off warning light airbag passenger (PAD) and lights warning light activated airbag passenger (PAE) (2008-).
The front passenger airbag switch and occupant weight sensor (OWS) must not both be installed in the vehicle.
DEACTIVATING/ACTIVATING AIRBAG PASSENGER FRONT (ONLY USA/CDN)
Under normal conditions, information from the occupant weight sensor (OWS) system (7/93) determines whether the supplemental restraint system module (SRS) (4/9) will disable or enable the front passenger airbag (8/124). The occupant weight sensor (OWS) is in constant communication with the supplemental restraint system module (SRS) via an internal CAN. If the front passenger seat has an occupant whose weight exceeds a certain limit value, the occupant weight sensor (OWS) informs the supplemental restraint system module (SRS) of such. The control module software then enables the front passenger airbag, giving it full functionality in the event of a collision. The supplemental restraint system module (SRS) then also deactivates the passenger airbag warning lamp (PAD) (10/22).
If the weight in the passenger seat front is below a certain level, the Occupant weight sensor (OWS) will inform the Supplemental restraint system module (SRS) about thins. Then the control module's software deactivates airbag passenger front, which means that the airbag remains inactive in case of a collision. Supplemental restraint system module (SRS) also lights warning light airbag passenger (PAD).
The front passenger airbag switch and occupant weight sensor (OWS) must not both be installed in the vehicle.
THE OCCUPANT WEIGHT SENSOR (OWS) SYSTEM (ONLY USA/CDN)
Occupant weight sensor (OWS) is designed to meet the legal requirements in Federal Motor Vehicle Safety Standard (FMVSS) 208 as well as to deactivate (make inflation impossible) the airbag on the passenger side front under certain conditions.
The occupant weight sensor (OWS) works with sensors that are part of the front passenger's seat and safety belt. The sensors are designed to detect the presence of a properly seated occupant and determine if the passenger's side front airbag should be enabled (may inflate) or disabled (will not inflate).
The occupant weight sensor (OWS) will disable (will not inflate) the passenger's side front airbag when:
- the front passenger seat is unoccupied, or there are small/medium objects in the front passenger seat,
- the system determines that an infant is present in a rear-facing infant seat that is installed according to the manufacturer's instructions,
- the system determines that a small child is present in a forward-facing child restraint that is installed according to the manufacturer's instructions,
- the system determines that a small child is present in a booster seat,
- a front passenger takes his/her weight off of the seat for a period of time,
- a child or a small person occupies the front passenger seat.
The occupant weight sensor (OWS) uses a passenger airbag warning lamp (PAD) which will illuminate and stay lit to remind you that the passenger's side front airbag is disabled. The passenger airbag warning lamp (PAD) is located in the overhead console.
Warning light airbag passenger (PAD) will be lit for a short time when the ignition is turned on to confirm that it also works for adult passengers.
When nobody is in the front passenger seat (empty seat) the airbag on the passenger side front will be deactivated. Then warning light airbag passenger (PAD) will be lit.
In case the airbag on the passenger side front is activated (inflation possible), then warning light airbag passenger (PAD) will not be lit.
The occupant weight sensor (OWS) is designed to disable (will not inflate) the passenger's side front airbag when a rear facing infant seat, a forward-facing child restraint, or a booster seat is detected. The passenger airbag warning lamp (PAD) will illuminate and stay lit to remind you that the passenger's side front airbag is disabled.
Volvo recommends that children always be properly restrained in appropriate child restraints in the rear seats.
Do not assume that the airbag on the passenger side front is deactivated unless the warning light airbag passenger (PAD) is lit.
The occupant weight sensor (OWS) is designed to enable (may inflate) the passenger's side front airbag anytime the system senses that a person of adult size is sitting properly in the front passenger seat. The passenger airbag warning lamp (PAD) will be unlit and stay unlit.
Occupant weight sensor (OWS) detects the pressure on the cushion in the passenger seat front as a result of the load in the seat. Occupant weight sensor (OWS) classifies the passenger as small or large based on if the caused pressure is above or below a certain pre-determined threshold value. The threshold value is given between a pressure caused by children and a pressure caused by adults according to legal requirements in Federal Motor Vehicle Safety Standard (FMVSS) 208. If the Occupant weight sensor (OWS) determines classification of a small passenger, the airbag on the passenger side front will be deactivated and warning light airbag passenger (PAD) will be lit. If the Occupant weight sensor (OWS) determines classification of a large passenger, the airbag on the passenger side front will be active and warning light airbag passenger (PAD) will be off.