Description And Operation
DESCRIPTION
The steering gear (2) is a rack and pinion type with Electric Power Steering (EPS). It is mounted on the front suspension sub cradle (3) by four mounting bolts (1). The only serviceable parts of the steering gear are the inner tie rods, outer tie rods, and the inner tie rod bellow. The EPS is connected to the vehicle wiring by three electrical connections from the torque sensor, power connection, and the module connection.
Do NOT disconnect the Torque Sensor (Grey) harness connector and make sure it is connected properly.
The EPS system is only serviced as an assembly.
If a NEW steering gear is installed, programming is required . Refer to EPS VERIFICATION TEST .
OPERATION
Turning of the steering wheel is converted into linear (side-to-side) travel through the meshing of the helical pinion teeth with the rack teeth within the steering gear. The lateral travel pushes and pulls the tie rods to change the direction of the vehicle front wheels. The EPS software has the ability to compensate for drift or pull caused by road crown and cross wind stability issues to keep the vehicle driving straight by monitoring the torque sensor inputs and applying torque to cancel out undesirable inputs.
The EPS supports the following features:
- Lane Departure Warning (Lane Sense) system by receiving directional torque request from the Forward Facing Camera (FFC), which helps keep the vehicle in the lane.
- Parallel/Perpendicular Park Assist (Parktronics) system by receiving steering torque request from the Park Assist Module (PAM) to rotate steering wheel during parking maneuvers.
Power assist steering is provided by an electric motor and control unit connected to the steering gear. The EPS system provides variable assist for steering maneuvers based on several inputs:
- Steering wheel position and rate of movement from the Steering Angle Sensor (SAS)
- Steering wheel torque from torque sensors in the EPS Gear
- Vehicle speed from the ESC module over Controller Area Network - Chassis (CAN-C)
The EPS system communicates over the CAN network. The Engine Control Unit (ECU) will display an EPS ICON on the cluster if it detects an abnormal condition, the fault codes may be retrieved using the scan tool, refer to the appropriate service information for additional diagnostic information.
The power for the EPS motor is provided though the PDC at terminal F1 protected by a 70 amp integrated fuse. The ground circuit is part of the engine harness grounded at the top of the transmission G907.
No components of the EPS system can be serviced separately. If any component of the EPS requires service, the entire steering gear must be replaced. The only serviceable parts are inner and outer tie rods, and tie rod bellows.
Manual steering control of the vehicle can be maintained if power steering assist is lost. However, under this condition, steering effort is significantly increased.