Speed sensitive power steering
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2007 Volvo V70, 2006 Volvo V70, 2005 Volvo V70, 2004 Volvo V70, and 2003 Volvo V70. However, it is still accessible from the selected car via links, so may be relevant.
If the car has speed dependent power steering to control the steering assistance, there is a solenoid which controls a hydraulic valve on the steering gear.
The solenoid is controlled by the power steering control module. This receives speed data from the directly connected speed signal from the central electronic module (CEM).
The power steering control module uses a signal to check the solenoid. The solenoid deploys the valve on the steering gear to the required degree and regulates the oil in the steering gear to reduce or increase the servo assistance. The steering assistance increases at lower speeds and is reduced at higher speeds.
There are no diagnostics for the power steering.