HONDA 2004 Civic Sedan - Owner's Manual - Manual (Page 206)

The exhaust emissions controls
include three or four systems: PGM-
FI, Ignition Timing Control, Exhaust
Gas Recirculation (SOHC VTEC
engine only), and Three Way
Catalytic Converter. These three or
four systems work together to
control the engine’s combustion and
minimize the amount of HC, CO, and
NOx that comes out the tailpipe. The
exhaust emissions control systems
are separate from the crankcase and
evaporative emissions control
systems.
The PGM-FI System uses sequential
multiport fuel injection.
It has three subsystems: Air Intake,
Engine Control, and Fuel Control.
The Engine Control Module (ECM)
or the Powertrain Control Module
(PCM) uses various sensors to
determine how much air is going
into the engine. It then controls how
much fuel to inject under all operat-
ing conditions.
This system constantly adjusts the
ignition timing, reducing the amount
of HC, CO, and NOx produced.
The Exhaust Gas Recirculation
(EGR) system takes some of the
exhaust gas and routes it back into
the intake manifold. Adding exhaust
gas to the air/fuel mixture reduces
the amount of NOx produced when
the fuel is burned.
The three way catalytic converter is
in the exhaust system. Through
chemical reactions, it converts HC,
CO, and NOx in the engine’s exhaust
to carbon dioxide (CO ), nitrogen
(N ), and water vapor.
The emissions control systems are
designed and certified to work to-
gether in reducing emissions to
levels that comply with the Clean Air
Act. To make sure the emissions
remain low, you should use only new
genuine Honda replacement parts or
their equivalent for repairs. Using
lower quality parts may increase the
emissions from your vehicle.
The emissions control systems are
covered by warranties separate from
the rest of your vehicle. Read your
warranty manual for more informa-
tion.
2
2
Emissions Controls
Technical Inf ormation
Exhaust Emissions Controls Replacement Parts
PGM-FI System
Ignition Timing Control System
Exhaust Gas Recirculation (EGR)
System
Three Way Catalytic Converter
203
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