Lincoln Aviator: Power Steering / Description and Operation - Adaptive Steering - System Operation and Component Description

System Operation

System Diagram

Network Input Message Chart

  SECM Network Input Messages

Adaptive Steering System

The SECM controls the functions of the adaptive steering system and communicates with other modules through the SASM over the HS-CAN2. The SECM and the SASM communicate over a private CAN.

To activate, the SECM requires the following:

• Battery voltage
• Ignition voltage
• Communication with other modules over the HS-CAN2
• Power pack status message from the PCM

The SECM uses a motor to turn a toothed hub connected to the steering shaft to add or subtract incremental turns to the driver steering shaft input. At low speeds the same steering input from the driver delivers more front wheel angle, providing more low-speed agility. Low speed maneuvers require significantly less steering wheel rotation. At high speeds, straight line driving precision is increased, providing the driver with an improved highway driving experience and feel during moderate-to-high-speed cornering.

As the driver turns the steering wheel, the SASM detects the speed and direction of the steering wheel rotation and transmits this information to the SECM over a private CAN. The SECM responds by activating the motor in the appropriate direction and speed to change the turning ratio of the front wheels, thereby reducing the necessary number of steering wheel turns required by the driver.

The SECM is self-monitoring and is capable of setting and storing Diagnostic Trouble Codes (DTCs). Depending on the nature of the DTC set, the SECM may send a request to the IPC to illuminate the adaptive steering system warning indicator and display a message in the message center, alerting the driver of a potential adaptive steering system concern. The warning message is sent over the HS-CAN2 to the GWM where it is converted to a HS-CAN3 message and sent to the IPC over the HS-CAN3.

Adaptive Steering Lock

The adaptive steering system is designed with a locking device. While the lock is engaged, the adaptive steering system is set to a fixed (1:1) steering ratio. A sound may be heard when starting or turning off the vehicle as the lock is disengaged or engaged, a slight movement of the steering wheel may be noticed while the locking action is taking place. If the vehicle loses electrical power or the SECM detects a fault while driving, the lock is engaged. Extreme operating conditions may also cause the SECM to engage the lock. This strategy prevents overheating and permanent damage to the adaptive steering system. Typical steering and driving maneuvers allow the system to cool and return to normal operation. While the lock is engaged, it is possible the steering wheel may not be straight when the vehicle is driving straight ahead and the driver may notice the steering wheel angle or clear vision may be offset.

The locking solenoid also engages when the ignition is set to ON and the driver door is closed, this prevents the steering wheel from turning unnecessarily while the system is off and affecting steering wheel clear vision. The locking solenoid disengages once the engine is started.

Heated Steering Wheel

The SECM is also the controlling ECU for the heated steering wheel system. For additional information on heated steering wheel,
Refer to: Steering Wheel and Column Electrical Components - System Operation and Component Description (211-05 Steering Wheel and Column Electrical Components, Description and Operation).

Component Description

Adaptive Steering Locking Solenoid

The locking solenoid is a normally engaged (locked) solenoid which requires a voltage input to disengage (unlock). This provides a fail-safe in case of SECM or adaptive steering system failure.

Adaptive Steering Motor

The adaptive steering motor is a reversible, variable speed motor with an attached worm gear. The motor is internal to the steering wheel and is serviced with the steering wheel.

SECM

The SECM contains the ECU for the adaptive steering system. The ECU monitors all sensor inputs and HS-CAN2 messages relating to the adaptive steering system and directly controls the output of the adaptive steering motor. The SECM is internal to the steering wheel and is serviced with the steering wheel.