Circuit/System Description

The motorized seat belt retractor motor modules are motorized seat belt pretensioners that operated independent from each other, and from the inflatable restraint sensing and diagnostic module. The motorized seat belt retractor motor modules normally remove slack from the seat belt, and under certain conditions apply tension to the seat belt of the driver seat, and if occupied, the passenger seat as well. A motorized seat belt is a seat belt with a motor coupled to the shoulder belt retractor. The motor performs a reversible, pretightening action (retraction) to reduce the slack in the seat belt. The motorized seat belt provides the driver and passenger a sense of safety and, in the case of severe braking or a crash, more quickly couples the occupant to the vehicle, enhancing the safety to the occupant.

Motorized seat belts monitor vehicle information to determine when to perform each of the following retractions

• Full retraction for such situations but not limited to: panic braking and or skidding
• Dynamic support for lateral and longitudinal dynamics
• Slack removal when the vehicle speed above enable speed

Preconditions for motorized seat belt retractions

• Seat belt buckle is latched
• Vehicle speed greater than or equal to 25 kph (16 mph)
• All messages on serial data are received as valid

Triggers that may cause motorized seat belt retractions

• Emergency Braking
• Sudden Emergency/Panic Braking
• High Vehicle Deceleration Detection
• Ice Braking Detection
• Oversteer and Understeer

Motorized seat belt inputs

• Vehicle Power Mode
• Transmission Gear
• Wheel Speeds
• Vehicle Acceleration
• Accelerator Pedal Position
• Steering Wheel Angle and Gradient
• Yaw Rate and Lat/Long Acceleration
• Brake Pedal Position, Gradient, Pressure, Initial Travel
• Vehicle Stability

Motorized seat belt output signals

• Driver information center message - motorized seat belt Failed "Service Automatic Seatbelt Tightening"
• Driver information center message - motorized seat belt Unavailable "Automatic Seatbelt Tightening Unavailable"

Motorized seat belt retractions are inhibited when seat belt unbuckled

Driver and passenger motorized seat belts operate independently