Operation

OPERATION

The Steering Angle Sensor (SAS) is part of the clockspring. The SAS detects steering wheel direction, angular magnitude, and rotational velocity, and transmits this data over the vehicle high speed serial communication bus (CAN-C). The SAS is a LIN bus master for the Multi Function Switch (MFS), and for switches that are mounted on the steering wheel (except for cruise control switches). The SAS is the gateway for the LIN bus data, and will transmit this data (switch status, including front wiper, turn signal, cruise control, EVIC) to the CAN-C bus. The SAS shall go into a "Sleep Mode," with ignition off, and shall "Wake Up" and transmit switch position when the flash to pass and horn functions are actuated. The SAS has dedicated inputs for the decoding of the cruise control switch functions. The cruise control switches are resistor multiplexed (RMUX), and are a "Dual Ladder" type of design. The SAS has primary and backup microprocessors (Master and Slave) to calculate steering angle and cruise control switch functionality. The SAS is able to detect a faulted condition and set a Diagnostic Trouble Code and transmit a Signal Not Available (SNA). The MFS and steering wheel LIN communications do not require redundant calculations. The clockspring portion of this assembly provides circuitry for the steering wheel mounted switches, and the driver airbag inflators.

The steering wheel rotational direction message that the SAS sensor sends out across the CAN-C is one of the following: counterclockwise is positive and clockwise is negative. The neutral or centered position is with the front wheels straight and the steering wheel at top dead center. Rotating the wheel to the left sends a positive value across the CAN-C and rotating the wheel to the right sends a negative value.

The SAS provides steering angle input data to the Electronic Stability Control (ESC) system when the ignition switch is in RUN Position.