System Diagram

Courtesy of NISSAN

INPUT/OUTPUT SIGNAL 

It transmits/receives each signal from the following pre-crash seat belt control unit via CAN communication line:

Component	Function
Steering angle sensor	Mainly transmits the following signals to pre-crash seat belt control unit LH via CAN communication: Steering angle sensor signal Steering angle speed sensor signal Steering calibration signal
BCM (Body Control Module)	Mainly transmits the following signals to pre-crash seat belt control unit LH via CAN communication: Ignition ON signal Sleep wake up signal Door switch signal
Combination meter	Mainly transmits the following signals to pre-crash seat belt control unit LH via CAN communication: Vehicle speed signal
ADAS (Advanced Driver Assistance System) control unit	Mainly transmits the following signals to pre-crash seat belt control unit LH via CAN communication: FED operation signal
ABS (Anti-lock Braking System) actuator and electric unit (control unit)	Mainly transmits the following signals to pre-crash seat belt control unit LH via CAN communication: ABS operation signal
Air bag diagnosis sensor unit	Mainly transmits the following signals to pre-crash seat belt control unit LH via CAN communication: Pre-roll over signal Pre-tensioner operation signal
Front seat belt buckle switch	Mainly transmits the following signals to pre-crash seat belt control unit LH: Front seat belt buckle switch signal

SYSTEM DESCRIPTION 

The pre-crash seat belt system integrates a control unit and motor in the existing seat belt pre-tensioners for both the driver and front passenger. The motor retracts the seat belt and secures the occupant during non-collision operations. The system integrates various CAN signals from other safety systems to give the driver and passenger a sense of security during various driving conditions. The motor extracts and retracts the seat belts when fastening to reduce effort required.

FUNCTIONS 

Pre-crash seat belt system may operate under the following conditions:

• Emergency brake operation
• ABS operation (extended)
• Forward emergency braking operation
• When lateral slippage during cornering occurs
• During emergency steering operations
• When the vehicle is inclined excessively
• When comfort function operates (refer to table below for more details)

OPERATING CONDITIONS 

Operating condition	Operation starts	Operation stops
Emergency brake operation	Vehicle speed is 9 MPH (15 km/h) or more Emergency braking status is detected	During acceleration Vehicle stopped
ABS operation (extended)	ABS operates continuously for 2 seconds or more Brake pedal is depressed
Forward emergency braking operation	System detects that forward emergency braking is operating	2 seconds after operation start
When lateral slippage during cornering occurs	Vehicle speed is 19 MPH (30 km/h) or more System detects that the vehicle is in lateral slippage state System detects that the vehicle is driving on a curve	Vehicle stopped 1 second or more after maintaining steering wheel angle in straight driving state
During emergency steering operations	Vehicle speed is 36 MPH (60 km/h) or more Steering wheel angle is 90 degrees or more System detects that steering wheel is rotated for emergency
When the vehicle is inclined excessively	Vehicle speed is 19 MPH (30 km/h) or more System detects that the vehicle inclined excessively	During acceleration Vehicle stopped

COMFORT FUNCTION 

Seat belts are extracted and retracted as shown in the following table:

Operating condition	Activation requirements	Comfort action	Deactivation requirements
Door is opened	Vehicle stopped Seat belt is unbuckled	Seat belt motor retracts belt	Seat belt retract is complete (maximum 13 seconds)
Seat belt is buckled	Door is closed	Seat belt motor extracts belt	Seat belt is unbuckled (maximum 1 second)
Seat belt is unbuckled	Seat belt is unbuckled	Seat belt motor retracts belt	Seat belt retract is complete (maximum 10 seconds)

CONDITIONS THAT PROHIBIT OPERATION 

Pre-crash seat belt system will not operate if the following conditions are detected:

• Motor overheat due to prolonged operation*
• Fail-safe mode activation

* System operation is temporarily deactivated to avoid overheating if system is continuously activated (18 times or more) during a short period of time.

MALFUNCTION WARNING 

When system malfunction is detected a warning message is displayed in the color display.