Exhaust Aftertreatment System (Eats) Overview - PREVOST H3-41 Maintenance Manual

SECTION 04 : EXHAUST AND AFTERTREATMENT
2. EXHAUST AFTERTREATMENT SYSTEM
(EATS) OVERVIEW
FIGURE 1: EXHAUST SYSTEM
The technology behind clean emissions is
through the immediate aftertreatment of engine
exhaust. The process for reducing NOx via
aftertreatment is called
Reduction (SCR). It requires a catalytic converter
into which is injected Diesel Exhaust Fluid
(DEF). The primary component of DEF is water;
the active component is urea. Urea is a nitrogen
compound that turns to ammonia when heated.
When a urea-and-water solution is injected into
the exhaust stream and passed over a catalyst,
the urea reacts with the NOx to form nitrogen
and water vapor – two clean and harmless
components of the air we breathe. The
aftertreatment system primary function is to
capture and oxidize (regenerate) the particulate
matter (soot) in the engine exhaust gases and to
reduce NOx. To achieve this goal, the exhaust
aftertreatment system (EATS) is split into two
main sections: the exhaust gases first enter the
Diesel Oxidation Catalyst (DOC) and Diesel
Particulate Filter (DPF) assembly to capture
and regenerate the soot on a regular or passive
basis, then the exhaust gases flow through the
catalytic converter to reduce NOx to minimum
level. Through constant monitoring of the
exhaust gas temperature and the system back
pressure, the Engine management System
(EMS) is able to manage regeneration.
10 PA1621 Maintenance Manual All Series | Section 04 revised Feb 2019
Selective Catalytic
The EATS is rubber mounted to the vehicle
structure. This feature reduces the transmission
of vibrations to the EATS thus resulting in
extended life of the system, brackets and also
noise reduction.
IMPORTANT NOTE
Exhaust Aftertreatment
components must not be removed, altered or
modified in any way. In order to protect the
emission control system from tampering,
inducement measures
following states are detected:
• Disconnection of DEF tank level sensor
• Blocked DEF line or dosing valve
• Disconnection of NOx sensor
• Disconnected exhaust temperature
sensor
• Disconnected DEF temperature sensor
• Disconnected DEF quality sensor
• Disconnection of DEF dosing valve
• Disconnection of DEF pump
Disconnection of SCR wiring harness
•
Auxiliary Emission Control Device (EACD)
defines as any element of design which
senses temperature, vehicle speed, engine
RPM, transmission gear, manifold vacuum, or
any other parameter for the purpose of
activating, modulating,
deactivating the operation of any part of the
emission control system.
Disconnection of the
produces immediate activation of the
Malfunction Indicator Lamp MIL and 25%
engine derate after three (3) hours of a
continuous open circuit.
• Intake throttle position sensor;
• Ambient air temperature sensor;
• Vehicle speed;
• Engine oil pressure sensor;
• Exhaust back pressure sensor;
• Camshaft speed sensor;
• EGR delta pressure;
• Fuel rail pressure
System (EATS)
will occur if the
delaying, or
following EACD