Once the engine has stopped, the DEF pump will
continue flowing in cooling mode to keep the DEF
injector cool. Then the DEF pump will proceed to a
purge mode. The DEF injector will remain closed.
The DEF pump will reverse the flow of the pump and
purge the supply, pressure, and return line. This
reversed flow will route any remaining DEF fluid back
to the tank.
Refer to Operation and Maintenance Manual for the
correct procedure to replace the DEF filter.
Electric Components of the DEF
System
The electric components of the DEF system consist
of the following components:
Coolant Diverter Valve
Controls coolant flow to the tank and DEF pump.
Dosing Control Unit (DCU)
This Dosing Control Unit (DCU) is an ECM that
controls all the electrical components in the DEF
system. While an ECM, this dosing control module is
referred to as the DCU. The DCU receives signals
from the engine Electronic Control Module (ECM).
Heated Lines
The heated lines are electrically heated lines that will
turn on any time the ambient temperature is cold.
These lines will thaw frozen DEF after starting in cold
ambient temperatures. The heated lines will also stay
heated during operation to prevent any freezing
during operation.
DEF Level Sensor
The level sensor will measure the amount of DEF in
the tank. The system uses an ultrasonic level sensor
to determine the amount of DEF in the DEF tank. To
measure the level of DEF, the sensor measures the
distance to the surface of the fluid. The sensor
provides a signal to the DCU that will be converted
into a “DEF Level Percentage” .
DEF Tank Temperature Sensor
This sensor is at the bottom of the tank and is
integrated within the DEF Level Sensor.
DEF Tank
The DEF tank stores the DEF. The size of the DEF
tank will depend on the application.
The DEF solution is made of 32.5 percent urea
solution and 67.5 percent deionized water. Urea is a
compound of nitrogen that turns to ammonia when
heated.
Ensure that the correct specification of DEF is used.
Refer to Operation and Maintenance Manual for
more information.
DEF does degrade over time at elevated
temperatures. Due to freezing risk, the tank, pump,
and lines must be heated and designed to contain
frozen DEF.
DEF Tank Header
Illustration 26 g03708818
Typical example
(1) Coolant tubes
(2) DEF pickup tube
(3) DEF tank header filter
(4) DEF tank temperature sensor, level sensor, and quality sensor
The DEF tank header is located in the DEF tank. The
tank header consists of several parts and performs
the following functions:
Coolant Tubes
32 UENR4490-01
Engine Operation
This document has been printed from SPI2. NOT FOR RESALE
To Next Page
Loading...
