Steering System: Other Ford Escape I рестайлинг 2

Electronic Power Assist Steering (EPAS) System

The Electronic Power Assist Steering (EPAS) system consists of the following components

1. Power Steering Control Module (PSCM) - the PSCM controls the functions of the EPAS system and communicates with other modules that are on the High Speed Controller Area Network (HS-CAN) bus. The PSCM is attached to the EPAS column assembly and is not available separately for service.
2. Motor - the EPAS gear uses a 12-volt brushless, reversible motor, a worm gear and a reduction gear to control the steering effort. The motor is attached to the EPAS column assembly and is not available separately for service.
3. Steering sensor - the steering sensor is used by the PSCM to determine force applied to, speed and direction of the steering wheel. This information is transmitted to other modules along the HS-CAN bus. The sensor is attached to the EPAS column assembly and is not available separately for service.
4. Steering column shaft - the steering column shaft connects the EPAS column assembly to the steering gear and is available separately for service. Refer to «STEERING COLUMN»(ref-344094) .
5. Steering gear - the steering gear is a rack and pinion type gear, which is serviced as an assembly and is contained within a one-piece aluminum housing. The steering gear uses tie-rod ends to connect the gear to the wheel knuckles. The steering gear can be serviced separately from the EPAS column assembly, refer to «POWER STEERING»(ref-344071) .
6. Tie-rod ends - one inner and outer tie rod is located at each end of the steering gear and are available separately for service. Refer to «POWER STEERING»(ref-344071) .

The EPAS system provides power steering assist to the driver by replacing the conventional hydraulic valve system with an electric motor coupled to the steering shaft. The motor is controlled by the PSCM which senses the steering effort through the use of a sensor mounted between the steering column shaft and the steering gear. Steering assist is provided in proportion to the steering input effort and vehicle speed.

Electronic Power Assist Steering (EPAS)

The Electronic Power Assist Steering (EPAS) system provides power steering assist to the driver by replacing the conventional hydraulic valve system with an electric motor coupled to the steering shaft. The motor is controlled by the Power Steering Control Module (PSCM) that senses the steering effort through the use of a torque sensor mounted between the steering column shaft and the steering gear. Steering assist is provided in proportion to the steering input effort and vehicle speed.

The EPAS system requires a 12-volt, hot at all times feed for system operation. The PSCM is activated when power is applied to the hardwired ignition/run input. After activation, the PSCM monitors the High Speed Controller Area Network (HS-CAN) bus to determine if the vehicle is operating in a manner capable of supporting the EPAS system.

The vehicle speed, which is sent by the PCM over the HS-CAN bus, provides the necessary information to the EPAS to determine the amount or level of power assist. As vehicle speed increases, the amount of power assist provided by the system is reduced to improve and enhance road feel at the steering wheel. If the vehicle speed is missing or out of range, the PSCM defaults to a reduced level of assist. If the vehicle speed returns to the correct in-range values, the PSCM adjusts the steering assist level accordingly.

Power Steering Control Module (PSCM)

The PSCM manages the EPAS system. The PSCM receives vehicle speed information from the PCM via the HS-CAN bus, the module also receives information from the steering shaft torque sensor to determine the amount of assist that is needed. At lower speeds, the control module will provide greater assist. At higher speeds, the control module will provide less assist. The PSCM is part of the steering column and is not serviceable separately.

The PSCM is self-monitoring and has the capability of setting and storing DTCs. Depending on the DTC set, the control module will enter into a "safe mode" and will provide a set amount of assist to the EPAS system.

Power Steering Motor

The EPAS system uses a 12-volt brushless reversible motor to control the steering effort. The motor is connected to the steering shaft through a worm gear and a reduction gear on the steering column. The motor is part of the steering column assembly and is not serviceable separately.

Steering Sensor

The steering sensor provides the PSCM with information on the direction, speed and amount of force being applied to the steering wheel. The module uses this information to determine the amount of steering assist required. The sensor is a 5-volt dual analog sensor with an output voltage range of 0.25 volt to 4.75 volts. When the steering wheel is turned to the left, the left signal increases while the right signal decreases, likewise when the steering wheel is turned to the right, the right signal increases while the left signal decreases.

Drift/Pull

Pull is described as a tugging sensation, felt by the hands on the steering wheel, that must be overcome to keep the vehicle going straight.

Drift describes what a vehicle with this condition does with the hands off the steering wheel.

1. A vehicle-related drift/pull, on a flat road, can cause a consistent deviation from the straight-ahead path and require constant steering input in the opposite direction to counteract the effect.
2. Drift/pull can be induced by conditions external to the vehicle (for example, wind or road camber).

Excessive Steering Wheel Play

Excessive steering wheel play is a condition in which there is too much steering wheel movement before the wheels move. A small amount of steering wheel free play is considered normal.

Lack of Assist or Inconsistent Assist

Lack of assist or inconsistent assist is experienced when the steering wheel effort is higher than normal. Hard steering can remain constant through the full turn or occur near the end of a turn. It is important to know the difference between hard steering/inconsistent assist and poor returnability/sticky steering.

Hard steering or lack of assist can result from either electrical or mechanical conditions.

Poor Returnability/Sticky Steering

Poor returnability and sticky steering is used to describe the poor return of the steering wheel to center after a turn or the steering correction, is completed.

Shimmy

Shimmy, as observed by the driver, is large, consistent, rotational oscillations of the steering wheel resulting from large, side-to-side (lateral) tire/wheel movements.

Shimmy is usually experienced near 64 km/h (40 mph), and can begin or be amplified when the tire contacts pot holes or irregularities in the road surface.

Wander

Wander is the tendency of the vehicle to require frequent, random left and right steering wheel corrections to maintain a straight path down a level road.

SYMPTOM CHART - STEERING SYSTEM

Steering Linkage

1. With the vehicle on the ground and the parking brake applied, start the vehicle and carry out the following: Have an assistant rotate the steering wheel back-and-forth 360 degrees and watch for the relative motion of the studs in the steering linkage ball sockets. Watch for loose steering gear mounting.
2. With the engine off, the steering wheel unlocked and the front wheels raised off the ground, grasp the wheel at the front and rear and watch for excessive play or binding in the joints while trying to steer the wheels. Grasp the inner tie-rod boot at the inner tie-rod socket and check for movement of the socket relative to the steering gear.
3. Install new components if necessary. Tighten any worn, damaged or loose components.