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PA1627 X3-45 Operator’s Manual

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SELECTIVE CATALYTIC REDUCTION UNIT

Selective Catalytic Reduction (SCR) is a
technology that uses Diesel Exhaust Fluid (DEF)
and a catalytic converter to reduce nitrogen
oxides (NOx) emissions.

SCR is an exhaust aftertreatment system that
injects small amount of DEF into the exhaust
gas between the DPF and the selective
reduction catalytic converter. DEF turns to
ammonia and carbon dioxide when heated. The
exhaust stream then passes over a catalyst, the
ammonia reacts with the NOx to form nitrogen
and water vapor.

The basic elements of the SCR system consist
of a 15.9 gallons (60 liters) DEF tank complete
with pump, lines and heating system, a dosing
injector, a catalytic converter and the control and
monitoring system.

DIESEL EXHAUST FLUID DEF

When handling DEF solution, keep electrical
connectors properly connected or well
encapsulated, otherwise there is a risk that the
DEF will cause oxidation that cannot be
removed. Water or compressed air will not help,
since DEF quickly oxidizes certain metals. If a
disconnected connector comes into contact with
the DEF solution, it must be replaced
immediately to prevent the DEF solution from
creeping further into the copper wiring, which
takes place at a speed of about 2.4 in (60 mm)
per hour.

CAUTION

Diesel Exhaust Fluid (DEF) is a nontoxic
aqueous solution of urea (32.5%) and ultra-
pure water (67.5%). Urea is a compound of
nitrogen that turns to ammonia when heated.
The fluid is non flammable, and is not
dangerous when handled as recommended.
However, it is highly corrosive to certain
metals, especially copper and brass.

When detaching hoses and components, do
not spill DEF on disconnected or unsealed
connectors. If DEF is spilled on a
disconnected or unsealed connector, the
connector must be removed immediately and
replaced.

Things to know about spilt diesel exhaust fluid
(DEF):



If urea solution comes into contact with the

skin, rinse with plenty of water and remove
contaminated clothing.



If urea solution comes into contact with the

eyes rinse for several minutes and call for
medical help if necessary.



If inhaled breathe fresh air and call for

medical help if necessary.



Do not allow the DEF solution to come into

contact with other chemicals.



The DEF solution is not flammable. If the

DEF solution is exposed to high
temperatures, it breaks down into ammonia
and carbon dioxide.



The DEF solution is highly corrosive to

certain metals, including copper and
aluminum.



If the DEF solution is spilled onto the vehicle,

wipe off the excess and rinse with water.
Spilled DEF solution can form concentrated
white crystals on the vehicle. Rinse off these
crystals with water.

WARNING

DEF spilt onto hot components will quickly
vaporize. Turn your face away!

Diesel Exhaust Fluid (DEF) Consumption

DEF consumption is related to fuel consumption.
In order to meet EPA2010 requirements, DEF
tanks are sized so one refill will be necessary
every two refill of the fuel tank.

SELECTIVE CATALYTIC REDUCTION –
DRIVER WARNING AND INDUCEMENT

SCR system components must not be removed,
altered or modified in any way. In order to
protect the SCR system from tampering,
inducement measures will occur if the following
states are detected:



Disconnection of DEF tank level sensor



Blocked DEF line or dosing valve



Disconnection of DEF dosing valve



Disconnection of DEF pump



Disconnection of SCR wiring harness