600SEL (140.057) V12-6.0L (120.980) (1993)
Steering Control Module: Description and Operation
NOTE: Numbers in parentheses ( ) indicate a component or tool in the associated illustration.
ELECTRONIC CONTROL UNIT (N49/1)
The electronic Parameter Steering (PML) control unit is accommodated in the module box (F23)
Exceptions: (Located under the right rear seat bench)
USA models with 6.0L/V12 (F23),
Californian version engines 3.2L/6 or 4.2L and 5.0L/V8
Its functions are divided up as follows:
-
Voltage Supply
-
speed Performance Map Control
-
Safety Circuit And Monitoring Device
-
Fault Memory
VOLTAGE SUPPLY
The PML control unit (N49/1) is supplied with battery voltage via the base module (N16/1) fuse F3
The operating voltage is in the range of 11-14 volts
Low voltages of less than 8.0 volts cause the PML to cut out; they are recorded by the fault memory and can be read out for diagnosis via pulse
output
After starting the engine, the function of PML is only taken over by the control unit when the alternator voltage is less than 8 volts
In this way the voltage supply and, due to the engine running, the drive of fire hydraulic pressure supply is confirmed
The voltage supply is permanently controlled by the monitoring device
SPEED PERFORMANCE MAP CONTROL
The vehicle speed is the input value for controlling parameter steering. The vehicle speed is assigned a nominal current value in a performance
map which is controlled at the PML P valve (Y10).
SAFETY CIRCUIT AND MONITORING DEVICE
There are two separate alternatives for deactivating the PML P valve (Y10) during fault detection by means of the monitoring device and safety
circuit
It is possible to shut off the valve from the positive and negative side
The monitoring device also checks the voltage supply (refer to the section on voltage supply)
FAULT MEMORY
The control unit is provided with a fault memory and is thus capable of diagnosis
Faults occurring remain stored even when the ignition is switched off and the battery is disconnected