400SEL (140.043) V8-4.2L (119.971) (1993)
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OPERATION
When the ignition switch is in the ON position, the idle speed control function is in operation. The position of the throttle valve for the idle speed
is determined by the control module via the nominal value potentiometer (accelerator pedal input) in the cruise control/idle speed actuator
(M16/2). The actual value potentiometer in the cruise control/idle speed actuator signals the position of the throttle valve. The cruise control/idle
speed control module compares the signals and specifies the position of the throttle valve via the output signal. This signal is used by the cruise
control/idle speed actuator to adjust the throttle valve.
Before starting the engine, the throttle valve position is determined by the engine temperature. Once the engine is running, the idle speed is
controlled by the cruise control/idle speed control module which provides a constant idle RPM, compensating for engine temperature and load.
The cruise control/idle speed control module uses the following information to determine the throttle position:
Input signals
^
Base module overvoltage protection (N16/1)
^
ABS control module (N30)
^
LH control module (N3/1)
^
EZL/AKR ignition control module (N1/3)
^
Cruise control/idle speed control actuator (M16/2)
^
Stop lamp switch (S9/1)
^
Starter lockout/backup lamp switch (S16/1)
^
Cruise control switch (S40)
^
A/C compressor engagement signal
^
Data exchange via controller area network (CAN)
^
Wheel speed sensors (L6/1 - L6/4)
^
Diode matrix (V2)
Output signals
^
Cruise control/idle speed actuator (M16/2 with throttle valve)
^
LH control module (N3/1)
^
Impulse readout (malfunction memory) via 38-pole diagnostic socket (X11/4)
^
Data exchange via controller area network (CAN)
Idle speed control function
The idle speed control function uses the following information to determine the correct idle speed:
^
Engine speed (TN-signal)
^
Coolant temperature
^
Vehicle speed signal
^
Selector lever position
^
A/C compressor engagement signal
Idle Speed/Temperature Chart
During idle, the control module keeps the engine speed at a constant RPM depending on engine coolant temperature.
