Steering

Steering





Steering gear
There are two types of steering gear, normal conventional power steering and speed related power steering.
Standard/option depending on variant/market.

Speed Sensitive Steering
The primary task for this system is to ensure that there is high power assistance for the steering when parking and at low speeds. To retain the road feel at higher sped the servo assistance decreases the faster the speed. This is achieved by varying the oil flow in the steering gear.
The oil flow is controlled, based on vehicle speed, by a step motor controlled by the central electrical module.

Stepper motor function
The stepper motor has the capacity to be moved an exact number of steps/rpm. This motor moves 48 steps/engine revolution. There is a conical control piston with an internal thread on the engine shaft which is screwed radially by the stepper motor. The central electrical module monitors the stepper motor position and resets it after every driving cycle.

Controlling power steering assistance
The conditions for activation are that the ignition key is in position 2 and engine speed is above 500 rpm. The signals are transmitted via the central electrical module.
At low speed the following occurs:
- Central electrical module supplies voltage to the stepper motor which begins to regulate, the piston on the rotor shaft moves and opens the return pipe on the steering gear which means that high servo assistance is achieved.
At high speed increase the central electrical module controls the stepper motor so that the position of the piston is changed every 5 km so that the steering becomes stiffer the faster one drives (the return pipe is choked). As speed is reduced the stepper motor reacts at 5 km/h (3 mph) intervals.
The vehicle speed signal to the central electrical module comes from the ABS sensor.

Fault messages, Diagnostics
If there is a fault in the system, dependent on the step motor, it remains in the position where the fault occurred.
A fault indication to the driver is displayed with both a warning lamp and a text message in the display. This information is a primary aid for workshop personnel when fault-tracing.
More thorough fault-tracing is carried out using VIDA.
- Read off/Erase diagnostic trouble codes (DTCs).
- Activate limit position step motor.

Note! In case of a fault in the stepper motor, valve housing or steering gear the complete unit must be replaced. (The steering gear is calibrated with the valve housing and stepper motor in the factory.)

Steering column
When the S/V70 was introduced a new type of steering column which collapsed at both the front and rear in a collision was used.
The steering column has modified mountings, but is otherwise the same.
The steering wheel is both radially and axially adjustable.
The lower steering shaft is telescopic, which means that it compresses in three stages, depending on the nature of the collision.

Note! No repairs to the steering column and steering shaft are permitted, they are replaced solely as a complete unit. When carrying out work on the front suspension which affects the lower steering shaft it must be disconnected. (There is a risk of damage to the telescopic joint).