Engine shutoff procedure, function

W07.15-1333-79

0 Ignition OFF

1 Circuit 15R ON

2 Circuit 15 ON

3 Kl.50

4 Engine CAN bus

5 Vehicle CAN bus

A3 Drive control (FR) control unit

A5 GGVS control unit**

A6 MR/PLD control unit

A7 Base module

A22 PSM control unit*

B15 Crankshaft angle position sensor

B16 Cylinder 1 TDC sensor

K2 Battery disconnect switch**

Z1 CAN star point cab dash support

* Vehicles with code (EM7) Parameterizable special module with body CAN bus or code (EM8) Parameterizable special module with body and trailer CAN bus

* * Vehicles conforming to German hazardous goods road transport regulations (GGVS)

S1 Drive switch

S5 Cab EMERGENCY OFF switch**

S11 Engine stop pushbutton switch

S109 Right frame EMERGENCY OFF switch**

Y1 Engine brake solenoid valve 1

Y6 Cylinder 1 unit pump

Y7 Cylinder 2 unit pump

Y8 Cylinder 3 unit pump

Y9 Cylinder 4 unit pump

Y10 Cylinder 5 unit pump

Y11 Cylinder 6 unit pump

Y49 Constant throttle solenoid valve
- only for vehicles with code (MZ4) Turbobrake

The engine can be stopped:

 with the drive switch (S1) using the ignition key

 with the engine stop pushbutton switch (S11)

 by means of the PSM control unit (A22) in the case of vehicles with code (EM7) Parameterizable special module with body CAN bus or code (EM8) Parameterizable special module with body and trailer CAN bus

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 on vehicles conforming to the German hazardous goods road transport regulations (GGVS), using the cab EMERGENCY OFF switch (S5) or using the right frame EMERGENCY OFF switch (S109)

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1 Stopping the engine with the drive switch (S1) using the ignition key
When the ignition key is turned to ignition OFF (0), the voltage supply (Tml. 15) at the MR/PLD control unit (A6) is interrupted by means of the drive switch (S1).
Interruption of the voltage supply (Tml. 15) means that the solenoid valves in the unit pumps will no longer be actuated. The total volume of fuel which the plunger-and-barrel assemblies deliver between the bottom dead center and top dead center is initially pushed into the respective diversion chamber and then into the return flow channel. The ejection pressure or the opening pressure of the injection nozzles is no longer achieved so there is no further fuel injection and the engine stops.

 The constant throttle valves in the cylinder heads are also actuated at the same time to accelerate the engine stopping process and to be more gentle on both the engine and the environment. Since these constant throttle valves can be hydraulically actuated or pneumatically actuated (depending on the vehicle equipment), the appropriate solenoid valve (for controlling the constant throttles) is actuated by either

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the MR/PLD control unit (A6) or the drive control (FR) control unit (A3):

 Vehicles with hydraulically actuated constant throttle valves (applies to vehicles with code (MZ4) Turbobrake):
These constant throttle valves are controlled by the constant throttle solenoid valve (Y49) which is actuated by the MR/PLD control unit (A6).

 Vehicles with pneumatically actuated constant throttle valves (applies to vehicles without code (MZ4) Turbobrake):
In this case, the engine control (MR) requests the drive control (FR) to actuate the engine brake solenoid valve 1 (Y1) since the compressed air is supplied to the constant throttle valves via this solenoid valve. The request is made by the MR/PLD control unit (A6) sending an appropriate message to the drive control (FR) control unit (A3) via the engine CAN bus (4); the drive control (FR) control unit then actuates the engine brake solenoid valve 1 (Y1) for as long as the request exists.

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 The length of time that the engine brake solenoid valve 1 (Y1) is actuated is determined by the engine control (MR).

When the engine stopping process has been completed, the MR/PLD control unit (A6) continues to be supplied with power from Tml. 30 for at least 10 seconds. This period, the so-called run-on phase, is used to write information to the permanent fault memory.

2 Stopping the engine with the engine stop pushbutton switch (S11)

 In order to prevent unintentional shutdown of the engine, the engine stop pushbutton switch (S11) must be held down until the engine has stopped. If the engine stop pushbutton switch (S11) is released before the engine speed has fallen below 50 rpm, the engine will start up again.

As soon as the engine stop pushbutton switch (S11) is pressed, the MR/PLD control unit (A6) interrupts actuation of the solenoid valves in the unit pumps.
As with the engine stopping process using the ignition key, the unit pumps feed the fuel

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directly into the return line, whereby injection is interrupted and the engine stops (as soon as the engine speed drops below 50 rpm).
When the engine has stopped, the MR/PLD control unit (A6) sends an appropriate "engine OFF" message via the engine CAN bus (4) to the drive control (FR) control unit (A3). This is because the drive control (FR) must be informed about the status of the engine in to be able to take this into account for its further calculations.

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3 Stopping the engine by means of the PSM control unit (A22)

 Only on vehicles with code (EM7) Parameterizable special module with body CAN bus or code (EM8) Parameterizable special module with body and trailer CAN bus.

The PSM control unit (A22) is connected to the drive control (FR) control unit (A3) via the vehicle CAN bus (5). If it sends an appropriate "engine OFF" message, this message is forwarded by the drive control (FR) control unit (A3) to the MR/PLD control unit (A6) via the engine CAN bus (4).

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The MR/PLD control unit (A6) interrupts actuation of the solenoid valves in the unit pumps which then causes the engine to stop.
The constant throttle valves in the cylinder heads will also be actuated when the engine is stopped by means of the PSM control unit (A22), as in the case of stopping the engine using the ignition key.
The MR/PLD control unit (A6) then enters the run-on phase in order to write information to the permanent fault memory.

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4 Stopping the engine with the cab EMERGENCY OFF switch (S5) or right frame EMERGENCY OFF switch (S109)

 Only on vehicles conforming to German hazardous goods road transport regulations (GGVS).

The cab EMERGENCY OFF switch (S5) and right frame EMERGENCY OFF switch (S109) are connected (in series) to the GGVS control unit (A5).
If the ignition key is at position Tml. 15R ON (1) or position Tml. 15 ON (2) and one of the two switches is actuated, then the GGVS control unit (A5) immediately interrupts the voltage supply (Tml. 30) to all consumers (except the voltage supply to the modular tachograph (MTCO)) by actuating the battery disconnect switch (K2).

Interruption of the voltage supply (Tml. 30) means that the solenoid valves in the unit pumps will no longer be actuated and the engine will stop.

 The EMERGENCY-STOP button must only be actuated in cases of danger and when the vehicle is stationary, but never when the vehicle is moving, otherwise it will no longer be controllable.