300SL (129.061) L6-3.0L (104.981) (1991)
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Electronic Throttle Control Module: Description and Operation
Electronic Accelerator Control Unit
Electronic Accelerator Control Unit
The electronic accelerator control unit (N4/1) contains two printed circuits with electronic components. On models 124 and 129 it is waterproof. The
housing consists of an aluminum alloy with a 35-pole plug connector. The connection with the wiring harness is through a 35-pole connection attached
with a spring bracket (arrow).
The electronic accelerator control unit supplies voltage to the potentiometers at the accelerator actuator and accelerator pedal position sensor. These
components return signals that are then processed. The electronic control unit is functionally divided into the following component groups:
^
System control with input amplifier (signal conditioning part),
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Output drivers,
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Monitoring equipment (safety circuit),
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Cruise control circuit,
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ASR signal processing.
The electronic accelerator control unit, with the exception of the cruise control circuitry, is designed as an analog processor.
SYSTEM CONTROL
The input signals to the system control are transformed, filtered and amplified in their respective signal conditioning components. Subsequently, these
signals are processed in the system control, which generates a specific signal for the output driver.
OUTPUT DRIVER
The output signal of the system control is sent to the output driver and there amplified. In addition, this signal determines the adjustment direction (open
or closed throttle) for the actuator DC motor.
If the DC motor is locked, a constant DC current is briefly applied. If it remains locked, then the control unit turns off the output driver. The output
driver is protected from short circuits to ground.
CRUISE CONTROL SYSTEM
The cruise control function is integrated into the electronic accelerator control unit. It is turned on or turned off by the cruise control switch. If the cruise
control switch is held on below approx. 40 km/h (25 mph) and the vehicle is then accelerated above that speed, the cruise control still does not turn on.
The cruise control also does not activate when the switch is turned on during braking. During SET cruise control driving, the system control unit receives
a corresponding input signal. This determines the setting of the throttle valve. If the driver exceeds the set speed using the accelerator pedal, the cruise
