SCR SYSTEM
The engine meeting requirements of Euro-4 ecology standards is installed on your truck.
Performance of Euro-4 requirements is provided due to the SCR system – injection of an
ammoniac solution to the engine exhaust system and transformations of harmful oxides of nitrogen
into nitrogen and water occurring at high temperature in the catalyst.
Components of the system: an AdBlue® tank, a pump module, a nozzle, a NO
x
sensor with
electronic unit, a temperature sensor, a solution heating system with electromagnetic valve (see
figure 27).
Principle of operation: urea is taken from the tank by the pump and forced into the nozzle. The
amount of urea injected into the engine exhaust pipe is monitored by the SCR unit and depends on
readings of temperature sensors of exhaust gases and
NO
x
. The SCR unit is connected with the
engine electronic control unit through the CAN cable.
It is necessary to watch the level of urea in the tank and indication of control lamps on the
dashboard: “yellow” and “red”.
During engagement of ignition the “yellow” lamp flashes on, after engine start-up it shall go
out, otherwise there is a malfunction in the SCR system. The “red” lamp flashes on when
malfunction of the engine in whole is registered, in case when it is blinking the level of ammoniac
solution in the system is minimal (amount of solution required for nozzle cooling).
Attention of the driver!
Absence of ammoniac solution in the AdBlue
®
tank can result in failure of the nozzle.
Absence of solution circulation in the pump module leads to non-fulfillment of Еeuro–4
requirements. In prospect, the manufacturer of engine plans to introduce a decrease of engine power
by 30–40% carried out by the engine control unit if there is no solution in the tank.
In winter heating of the system is controlled by the open air temperature sensor. All pipelines
from the tank to the pump module (from the pump module to the tank) and from the pump module
to the nozzle (from the nozzle to the pump module) have electrical heating. Heating of the tank and
pump module is carried out by means of circulation of coolant via them (upon reaching coolant
temperature of 65 C, a signal is given to the engine control unit which opens an electromagnetic
valve supplying a coolant to the SCR heating system).
Warming up of the system is only possible on the run (under load) and impossible at idling
engine.
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