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Individual functions - RA3000TPM0008X(30-0008)

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Overvoltage protection relay 

Models 124, 202 

Base module 

Models 124.034/036, 129, 140 

Additional outputs  :

Accelerator pedal/throttle control 

Applies to EA only 

The position of the accelerator pedal is input to the EA actuator via accelerator pedal, accelerator pedal lever, bowden cable, transfer lever and connecting rod. On engines 104 and 119, the mechanical actuation takes place at the actuator M16/1, and on engine 120 at the actuator M16/3. The actuator M16/4 is only actuated electrically.

The throttle valve is then adjusted via the electrical/electronic components such as the electronic accelerator control module and actuator.

The specified value potentiometer is operated by the output lever of the actuator via the spring capsule. The throttle valve is operated via the d.c. motor in the actuator due to signal processing in the control module. The adjustment travel ranges from the idle stop to the full throttle stop.

In the event of a fault in the electrical/electronic components, the throttle valve can be adjusted via the spring capsule. This ensures that the vehicle can be driven with approx. 2/3 engine output in the case of engines 104 and 119 and approx. 1/3 engine output in the case of engine 120.

Accelerator pedal idle speed contact switch 

The idle speed contact switch (S29/3) is open at idle. When the throttle is opened, initially the idle speed contact switch closes before a specified value can be changed at the actuator via the control system.

Fig 3: Identifying Idle Speed Contact Switch
G04684819Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

EA actuator 

The following are integrated in the actuator:

Engine 120 

Actuator for left cylinder bank (located on right of engine).

IMPORTANT

This actuator has no mechanical actuation but is only actuated electrically by the EA control module  .

The adjustment range of both actuators is 8° - 90° in each case.

The following components are included in the actuator:

Specified value potentiometer 

When the ignition is switched on or the engine is running, the specified value potentiometer is actuated by a constant voltage from the EA control module. The potentiometer position is changed via the throttle linkage by means of adjustment movement at the accelerator pedal. A defined, variable voltage is transmitted back to the EA control module by the potentiometer, depending on accelerator pedal position. This signal is processed further in the position controller of the control module.

Actual value potentiometer 

When the ignition is switched on or the engine is running, the potentiometer is actuated with a constant voltage from the EA control module. The output signal of the potentiometer to the control module is used as a position feedback of the instantaneous throttle valve position.

This signal is processed further in the position controller of the control module. The position of the throttle valve is varied by the control module in the event of deviating signal values.

Actual value potentiometer 2 

(engine 120 only. Actuator of left cylinder bank, located on the right of the engine)

In principle, the function of actual value potentiometer 2 is identical to that of actual value potentiometer of the actuator of the right cylinder bank. Adjustment is made electrically by the EA control module. The signal from the monitoring system is checked and is compared with the signal of the other actuator.

Actual value potentiometer 3 

(Engine 120 only. Actuator of left cylinder bank, located on the right of the engine)

In principle, the function of actual value potentiometer 3 is identical to that of the actual value potentiometer of the actuator of the right cylinder bank. The signal is used as a position feedback of instantaneous throttle valve position. This signal is also processed by the position controller and checked by the monitoring system.

Safety contacts 

  1. Idle speed safety contact 

    Signals the idle position of the throttle valve in the actuator to the EA control module. The idle safety contact is integrated in the lever which is permanently connected to the throttle valve. When the ignition is switched on or when the engine is running, a stabilized voltage is applied to the input side. The idle safety contact is closed when the accelerator pedal is not operated (idle position).

    The signal is checked via the monitoring system. If the signal evaluation is in order, an output signal to the LH-SFI or HFM-SFI control module takes place which then releases the actuation of the fuel pump. The switching point of the idle safety contact is 2 to 3° of adjustment above the idle stop. With the adjustment from full throttle towards idle, the idle safety contact closes at 4° of adjustment before the idle stop.

  2. Synchronous safety contact 

    Signals the driving position of the throttle valve.

    The synchronous safety contact is open when the accelerator pedal is not operated. It closes when the accelerator pedal is operated. The switching point is approx. 4° above the idle position.

    The signal is also checked via the monitoring system. The LH-SFI or HFM-SFI control modules are actuated as for the idle safety contact.

  3. Safety fuel shut-off 

    Shuts off the fuel supply in the event of faults in the actuator contacts.

    Normally a safety contact is always closed. If both contacts are open in the event of a fault, the LH-SFI or HFM-SFI control module receives a fault signal from the monitoring system in the EA or CC/ISC control module. This signal triggers the safety fuel shut-off, the engine speed being limited to approx. 1200 rpm.

    In cruise control mode, the synchronous safety contact is bridged by means of a switching transistor. Here an inadmissible acceleration is detected by monitoring the speed and acceleration plausibilities and the cruise control is switched off.

Actuator motor 

The actuator motor is actuated by the control module via the output stage with 140 to 160 Hz. As a result, the throttle valve can be adjusted from idle to full throttle (8-90° adjustment angle) via multi-stage gearing. The d.c. motor has a high adjustment speed.

The complete degree of adjustment is covered in approx. 120 ms. The power consumption at the maximum rate of adjustment is approx. 12 A.

Coupling 

The coupling is actuated from the monitoring system in the EA control module with a pulsed voltage signal (2 kHz). The maximum current value is 2.6 amperes.

The monitoring system switches off the coupling in the event of a failure of the electrical/ electronic control functions. The connection is released and the throttle valve can be adjusted mechanically. It is thus possible to continue driving with reduced engine output (limp-home mode).

Engine 120 

There is no mechanical connection between the actuator for the left cylinder bank (located on the right of the engine) and the accelerator pedal.

In the event of faults in the electrical/electronic control function, the throttle valve can no longer be opened via the accelerator pedal.

CC/ISC actuator 

The following are integrated in the actuator:

The adjustment range of the actuator is 8-90°. As a result, the throttle valve can be adjusted from idle speed to full throttle stop and vice-versa via the throttle linkage.

Between idle speed and full throttle the throttle valve is operated purely mechanically via the accelerator pedal lever.

Drive actual value potentiometer 

Throttle valve actual value potentiometer 

Idle contact 

Safety contact 

(on CC only)

Actuator motor 

The actuator motor is actuated by the control module via the output stage with 140 to 160 Hz and adjusts the throttle valve via multi-stage gearing.

Adjustment range 

Idle speed range 8-12°

Cruise control range 8-90°

The power consumption at maximum rate of adjustment is approx. 12 A.

Coupling 

The coupling is actuated by the monitoring system with a pulsed voltage signal (2 kHz) from the CC/ISC control module. The maximum current is 2.6 A.

ISC actuator 

The following are integrated in the actuator:

Drive actual value potentiometer 

Throttle valve actual value potentiometer 

Idle speed contact switch 

Actuator motor 

The actuator motor is actuated by the control module via the output stage with 140 to 160 Hz and adjusts the throttle valve via multi-stage gearing.

Adjustment range 4-8°

Coupling 

The coupling is actuated with a pulsed voltage signal (2 kHz) from the ISC control module. The power consumption at max. rate of adjustment is approx. 12 A.

EA, CC/ISC control module 

Individual functions 

Voltage supply 

When the ignition is switched on, the following components are supplied with voltage from the EA control module:

In addition, for the left actuator on engine 120, located on the right of the engine are:

Specified value selection 

The following signals are input:

The signals are evaluated and the signal with the highest priority determined  with the specified computer program. The position controller and the monitoring system are actuated by the output signal.

If the specified value signal deviates from the actual value signal, the D.C. motor is actuated via the output stage and the throttle valve position is changed. The adjustment continues until the specified and actual value agree.

At the same time the information available in the specified value selection are signalled to the data bus. It transmits it to the following components:

A signal is also sent directly to the LH-SFI or HFM-SFI control module by the nominal value selection. In conjunction with other information available from the LH-SFI or HFM-SFI control module, the period for actuation of the injection valves is calculated at idle speed.

Pedal characteristic maps 

(Accelerator pedal or cruise control requirement) The accelerator pedal position is input to the EA control module by the specified value potentiometer of the actuator. In addition, the following signals are also processed:

The appropriate characteristic map is actuated depending on the signals applied. Thus the output signal is transmitted on to the nominal value selection via the maximum value selection. There the signal is compared with others. The signal with the highest priority takes precedence and determines the position of the throttle valves via the position controller and the output stage. At the same time, the signals are checked by the monitoring system.

The pedal characteristic maps are designed to achieve throttle valve opening limitations at which the max. drive moment is still achieved.

ASR/EBR signal processing 

The ASR/EBR data are transmitted to the EA control module by the ABS/ASR control module via the data bus. The data are updated every 10 ms.

The ASR data are input to the minimum value evaluation and the EBR data in the maximum value evaluation. The output signal calculated during this process is input to the nominal value selection and evaluated with the other signals (idle speed control signal). The signal with the highest priority takes precedence and controls the position controller and thus the throttle valve via the output stage.

If no ASR/EBR signal or Cruise control signal is applied, the accelerator pedal position, or the idle speed control when the accelerator pedal is not operated, determine the position of the throttle valve.

Anti-squat control (engine 120 only) 

To protect the driveline, the EA control module controls the engine output moment below a speed threshold of 5 km/h to a particular limiting moment depending on the selector lever position D, 3, 2 or R. To effect this, the throttle valve is moved back towards the accelerator pedal position.

Load value limitation (engine 120 only) 

The EA control module receives a load value limitation signal from the ignition control module via the data bus. The signal is effective, if for example the fault "knock sensor defective" or "camshaft sensor implausible" is detected in the ignition control module. This results in the ignition being retarded whereby only a particular opening angle of throttle valve is permitted by the EA.

Maximum speed limitation (engine 120 only) 

The maximum speed is limited to 250 km/h. When this speed is exceeded, the throttle valve is closed irrespective of the accelerator position.

Speed signal 

After signal processing, the speed signal from the front left and rear left wheel speed is fed to the EA control module by the ABS/ASR control module. On model 124, engine 104 HFM-SFI, front left wheel speed and speedometer hall sensor signal.

The selector lever position is input by the starter lockout and reverse switch. The signals are evaluated, processed and transmitted at the data bus (CAN) and the cruise control and idle speed system.

Position controller 

Various input values are calculated to give an output value in the specified value selection unit. This output value is input to the position controller where it is compared to the actual value of the throttle valve position. In the event of deviations, corrections are made until the specified and actual value are the same.

Output stage 

The output signal of the position controller is transmitted to the output stage and amplified there. This signal furthermore determines the direction of adjustment  (idle speed or full throttle direction) of the d.c. motor in the actuator during idle speed and cruise control mode. At the same time the output stage is actuated by the monitoring system via the safety relay.

Both signals are compared in this process. If the signals are identical, the d.c motor is actuated at a frequency of 140 to 160 Hz. The clutch is also monitored by the monitoring system.

Monitoring and limp-home mode 

Safety functions are fulfilled by the monitoring system. Limp-home mode operates in the event of faults in the system (e.g if the throttle valve is opened more than specified by the accelerator pedal and cruise control is not in operation).

With mechanical limp-home mode  the output stage of the clutch and the actuator motor is switched off. The throttle valve can then only be adjusted mechanically via the accelerator pedal so that 2/3 engine output on engines 104 and 119 and 1/2 engine output on engine 120 are available (e.g. in the event of errors in the accelerator pedal idle speed contact switch).

With electronic limp-home mode  the engine speed is limited to approx. 1200 rpm via the injection system by controlling the fuel supply (safety fuel shut-off) (e.g. in the event of faults in the idle speed or synchronous safety contact).

The following functions are monitored:

Safety relay 

This is actuated by the monitoring system via the "Approval/disconnection" control module if the output signal is approved due to the signals applied. Both components control the output stage for the actuator motor. The coupling in the actuator is actuated by the monitoring system at the same time.

Data bus (CAN) 

(refer to chapter on data bus)

Idle speed control 

This is performed by the EA or CC/ISC control module. On vehicles with LH-SFI injection system, without EA or CC/ISC, a "separate" control module is responsible for idle speed control.

(For function, refer to chapter on ISC Function Description)

Cruise control 

The cruise control function is integrated in the EA control module.

(For function, refer to chapter on CC/ISC Function Description)

Fault memory/diagnosis 

All system components are monitored by the monitoring system in the EA, CC/ISC control module. Faults are stored in the fault memory of the control module and are retained after the battery is disconnected.

The stored faults can be read out and erased at the test coupling for diagnosis (X11/4) using the hand-held tester (HHT) or the pulse counter (for fault chart with details of fault codes, refer to Diagnosis Manual, Volume 3)

ABS/ASR control module 

Specified value requirement for throttle valve position in ASR or EBR mode, irrespective of accelerator pedal position 

Every 10 ms information is exchanged between the ABS/ASR control module and the EA control module via the data bus (CAN).

From the shape of the signal from the ABS/ASR control module, the EA control module detects when ASR or EBR intervenes and determines which maximum throttle valve opening is permissible. Irrespective of the slip conditions at the drive wheels, the throttle valve can be completely closed or briefly opened to a limited extent by means of an appropriate ASR/EBR control signal.

With the ASR control signal, it can also be closed if full throttle is specified by the driver or by the cruise control. By means of a similar type of feedback signal (throttle valve actual value) the EA control module informs the ABS/ASR control module continuously about the instantaneous position of the throttle valve. The ABS/ASR control module can thus check whether the EA follows the position commands of the ASR/EBR system during ASR/EBR control mode. If a fault exists in the area of the EA (without cruise control function) (actuator without voltage supply), the feedback signal disappears and the ASR switches to "fault". The ASR malfunction indicator lamp (A1e22) comes on.

Speed signal for EA or CC/ISC control module 

Allocation  :

for CC/ISC  : Speed sensor from left (L6/1) and speed sensor rear axle (L6)

Fig 4: Identifying Speed Sensor From Left
G04684820Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Fig 5: Identifying Speed Sensor Rear Axle
G04684821Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Engine 104 HFM-SFI, Model 124 

The speed signal for the rear wheels is not output from the ABS/ASR control module but picked up by a hall sensor on the speedometer and is used for the cruise control function as well as idle speed control.

Fig 6: Identifying Speed Signal - Engine 104 HFM-SFI, Model 124
G04684822Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

ASR/EA  : Front left (L6/1) and rear left speed sensor (L6/3).

The speed signals recorded by the speed sensors of the wheels or the speed sensor of the rear axle (with CC/ISC) are input to the ABS/ASR control module and transmitted by this to the EA or CC/ISC control module.

The speed signals are required for

HFM-SFI injection system control module 

Starter lockout and reverse lamp switch 

When engaging the drive position, the signal is evaluated. As a result the characteristic map is changed over. This signal is then passed on to the specified value selection.

Fig 8: Identifying Starter Lockout And Reverse Lamp Switch
G04684824Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

A/C compressor control module 

(Air conditioner)

When the refrigerant compressor is switched on, the control module receives a switch-on signal. On the models 129 and 140 this is from the base module, on models 124 and 202 from the A/C compressor control module.

The control module processes the applied voltage and transmits an appropriate signal to the specified value selection. The opening cross section increases before the refrigeration compressor cuts in so that the idle speed can be kept approximately constant.

Cruise control switch 

When the CC switch (S40) is operated, the EA or CC/ISC control module can receive the following commands:

Control contact switch 

This is closed when the switch is operated. The control contact is monitored in the EA or CC/ISC control module. The cruise control cannot be switched on in the absence of a control signal when the switch is operated. The cruise control can also be switched off in the absence of a control signal.

Stop lamp switch/clutch pedal switch 

When the brake or clutch is operated, the cruise control system receives a change in signal. The cruise control function is cancelled immediately.

The input signal of the cruise control system is cancelled at the position controller. As a result, the actuator is actuated so that the throttle valve is moved back to the specified value by the accelerator pedal. The position of the accelerator pedal has priority. Opening the throttle and also controlling the drive moment are not impaired.

Fig 10: Identifying Stop Lamp Switch/Clutch Pedal Switch
G04684826Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Diode matrix 

(Model 140 only, engine 119, 120 LH-SFI up to the end of 92)

The idle speed is increased from 550 rpm to 650 rpm under certain conditions to achieve a higher charge current at idle speed.

Idle speed increase is activated when drive stages D 3, 2 and 1 are engaged, if an engine speed of 900 rpm has been exceeded, one or more of the following appliances are switched on:

The idle speed increase is switched off when drive stages P, R or N are engaged and when the coolant temperature is ≥ 110°C. The EA or CC/ISC control module is actuated by the appliances via a diode matrix. The diode matrix prevents backflows to the other connected appliances if one or more appliances are switched on.

CHARGE CURRENT

Engine speed Generator speed Charge current
550 rpm 1595 rpm 47 A
650 rpm 1885 rpm 65 A
2180 rpm 6300 rpm 120 A

Data bus (CAN) 

The following control modules are interconnected using the data bus (CAN = Controller Area Network)

The control modules are interconnected by two cables.

As a result, additional sensors as well as inputs and outputs can be dispensed with on the control module. Data is constantly transferred in information blocks. If one control module transmits, the other control modules receive and vice versa. The control modules only receive the data which they require. Important data are transmitted as a priority (refer to data which are transmitted via the serial data line). If a limp-home function exists as a result of a fault indication, the function is retained by the data bus.

Fig 12: Data Bus (CAN) System
G04684828Courtesy of MERCEDES-BENZ OF NORTH AMERICA.

Transmission data (CAN) 

(shown on vehicle with LH-SFI injection system)

Fig 13: Transmission Data (CAN) System
G04684829Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
Fig 14: Transmission Data (CAN) System
G04684830Courtesy of MERCEDES-BENZ OF NORTH AMERICA.
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