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Summary of components of power-assisted steering TRW > < Power-assisted steering TRW
Structure and function
Structure and function
   
The EPHS (Electrically Powered Hydraulic Steering) is a power-assisted steering system which uses its own electric motor to drive the pump.
1 - Power-steering gear
2 - Sensor for power steering -G250-
3 - Steering column
4 - Control unit in dash panel insert -J285-
5 - Sender for speedometer -G22-
6 - Engine control unit
7 - Servotronic warning light -K92- in dash panel insert
8 - Signal for servotronic warning light -K92- via data BUS
9 - Signal for engine speed via data BUS
10 - Signal for driving speed via data BUS
11 - Hollow screw with non-return valve
12 - Pressure line
13 - Signal for steering angle speed
14 - Return-flow line
15 - Airbag control unit -J234-
16 - Crash signal over the databus
17 - Terminal +30
18 - Terminal +15
19 - Earth
20 - Engine pump aggregate - consisting of:
a - Screwed lid
b - Reservoir for hydraulic oil
c - Pressure limiting valve
d - Gear pump
e - Electric motor
f - Power-assisted steering control unit -J500-
The steering hydraulics pump -V119- includes the gear pump -d- and the electric motor -e-.
The gear pump is integrated into the engine pump aggregate.
This gear pump -d- is driven by an electric motor -e- integrated into the engine pump aggregate.
Signals for steering angle speed -13-, for vehicle speed -10- and engine speed -9- are sent to the control unit -f-. This control unit controls the speed of the electric motor -e- on the gear pump and thus also the supplied quantity or volume of hydraulic oil.
Re-engaging protection
The electrohydraulic power-assisted steering has a re-engaging protection after faults, failure or crash.
After a crash or after the display of the crash signal on the vehicle diagnosis, measurement and information system -VAS- the vehicle memory must be erased to de-activate the re-engaging protection.
The re-engaging protection can be neutralised by switching off the ignition and switching it on again. If necessary wait 15 minutes to allow the engine pump aggregate to cool down after overheating. If after this waiting period the re-engaging protection cannot be neutralised by switching the engine on again, the fault must be found in the vehicle electric system or e.g. in the engine pump aggregate. In these instances perform the self-diagnosis and if necessary replace the engine pump aggregate.
  S48-0200

Summary of components of power-assisted steering TRW > < Power-assisted steering TRW