Engine shutoff procedure, function

W07.15-1442-79

0 Ignition OFF

1 Circuit 15R ON

2 Circuit 15 ON

3 Circuit 50

A3 Drive control (FR) control unit

A5 GGVS control unit 4)

A6 Engine control (MR) control unit

A7 Base module (GM)

A22 Parameterizable special module (PSM) control unit 3)

B15 Crankshaft position sensor

B16 Camshaft position sensor

CAN 1 Vehicle CAN

CAN 4 Engine CAN

K2 Battery disconnect switch 4)

S1 Drive switch

S5 Cab EMERGENCY OFF switch 4)

S10 Start engine button

1) Model 958 without code (XV0) Global Cockpit

2) Model 374, 375, 950, 952, 953, 954, 970, 972, 974, 975, 976;
model 958 with code (XV0) Global cockpit

3) Only for vehicles with code (EM8) Parameterizable special module with body and trailer CAN bus (ISO 11992) or code (EM9) Parameterizable special module with body and trailer CAN bus, ISO 11898 instead of 11992

4) Only for vehicles in accordance with the German hazardous goods road transport regulations

S11 Stop engine button

S109 Frame EMERGENCY OFF switch 4)

Y1 Pneumatic constant throttle solenoid valve
- Only for engine 900.9, 904.9, 924.9

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
- Only for engine 902.9, 906.9, 926.9

Y11 Cylinder 6 unit pump
- Only for engine 902.9, 906.9, 926.9

Y49 Hydraulic constant throttle solenoid valve
- Only for engine 902.9, 906.9, 926.9

Z1 CAN star point cab dash support

The engine can be stopped:

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

 with the Stop engine button, button (S11)

 via the parameterizable special module (PSM) control unit (A22)
 Only for vehicles with code (EM8) Parameterizable special module with body and trailer CAN bus (ISO 11992) or code (EM9) Parameterizable special module with body and trailer CAN bus, ISO 11898 instead of 11992

 by using the cab EMERGENCY OFF switch (S5) or the frame EMERGENCY OFF switch (S109)
 Only for vehicles in accordance with the German hazardous goods road transport regulations

1 Stopping the engine with the ignition key via the Drive switch (S1)
The voltage supply (circuit 15) at the engine control (MR) control unit (A6) is interrupted over the Drive switch (S1) after turning the ignition key to the position ignition OFF (0).
Interruption of the voltage supply (terminal 15) means that solenoid valves in the unit pumps will no longer be actuated. The total volume of fuel which the pump elements deliver between bottom dead center and top dead center is initially pushed into the respective diversion chamber and then into the return 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 engine), the appropriate solenoid valve (for controlling the constant throttles) is actuated by either

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

 Vehicles with hydraulically actuated constant throttle valves (applies to vehicles with engine 902.9, 906.9 and 926.9):
These constant throttle valves are controlled by the hydraulic constant throttle solenoid valve (Y49) which is actuated by the engine control (MR) control unit (A6).

 Vehicles with pneumatically actuated constant throttle valves (applies to vehicles with engine 900.9, 904.9 and 924.9):
In this case, the engine control (MR) requests the drive control (FR) to actuate the pneumatic constant throttle solenoid valve (Y1) since compressed air is supplied to the constant throttle valves via this solenoid valve.

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The request is made by the engine control (MR) control unit (A6) sending an appropriate message to the drive control (FR) control unit (A3) via the engine CAN (CAN 4); the drive control (FR) control unit then actuates the pneumatic constant throttle solenoid valve (Y1) for as long as the request exists.

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

The engine control (MR) control unit (A6) is supplied with power from terminal 30 for at least 10 s after the shut-off process has finished. This period, the so-called run-on phase, is used to write information to the permanent fault memory.

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 For vehicles with code (MS4) BlueTec 4 or code (MS5) BlueTec 5 the metering device is ventilated in the run-on phase (max. 300 s), whereby frost damage can be avoided through freezing AdBlue.
Ventilation of the metering device takes place through opening and closing the SCR air pressure limiter solenoid valve (Y106) and the SCR AdBlue metering valve (Y109) in defined intervals. The basic variables for the duration of the purging procedure are the pressure present at the SCR AdBlue pressure sensor (B129) and the pressure at the SCR compressed air pressure sensor (B128). Ventilation is only stopped only when the engine control (MR) control unit (A6) based in these values recognizes that the metering device was adequately filled with air.

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2 Stopping the engine using the Stop engine button button (S11)

 The Stop engine button button (S11) must continue to be pressed until the engine has stopped in order to prevent unintentional shutdown of the engine. If the Stop engine button button (S11) is released before the engine speed has fallen below 50 rpm, the engine will start up again.

As soon as the Stop engine button button (S11) is pressed, the engine control (MR) 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 directly into the

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Return line, whereby injection is interrupted and the engine stops (as soon as the engine speed drops below 50 rpm).
Once the engine has stopped, the engine control (MR) control unit (A6) sends an appropriate message over the engine CAN (CAN 4) concerning the stationary condition of the engine 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 via the parameterizable special module (PSM) control unit (A22)

 Only for vehicles with code (EM8) Parameterizable special module with body and trailer CAN bus (ISO 11992) or code (EM9) Parameterizable special module with body and trailer CAN bus, ISO 11898 instead of 11992.

The parameterizable special module (PSM) control unit (A22) is networked via the vehicle CAN (CAN 1) with the drive control (FR) control unit (A3). If it sends an appropriate message for stopping the engine then this is passed on by the drive control (FR) control unit (A3) via the engine CAN (CAN 4) to the

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Engine control (MR) control unit (A6).
The engine control (MR) control unit (A6) interrupts actuation of the solenoid valves in the unit pumps which 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 parameterizable special module (PSM) control unit (A22), as in the case of stopping the engine using the ignition key.
The engine control (MR) control unit (A6) then enters the run-on phase in order to write information to the permanent fault memory.

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4 Switching off the engine using the EMERGENCY-STOP button in the cab (S5) or by using the EMERGENCY-STOP button on the vehicle frame (S109)

 Only for vehicles according to GGVS.

The cab EMERGENCY OFF switch (S5) and frame EMERGENCY OFF switch (S109) are connected (in series) to the GGVS control unit (A5).
If the ignition key is in the position terminal 15R ON (1) or in the position terminal 15 ON (2), and of one of both switches is actuated then the GGVS control unit (A5) immediately interrupts the power supply (terminal 30) to all consumers through actuation of the battery disconnect switch (K2),

except the tachographs.
Interruption of the voltage supply (terminal 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.