Chrysler DODGE D150 1993 Service Manual page 1487

2 5 - 1 0 EMISSION CONTROL SYSTEMS
E X H A U S T E M I S S I O N C O N T R O L S
INDEX
page
Air Inlet—5.9L Diesel Engine 13
Exhaust G a s Recirculation ( E G R ) Systems 10
HEATED INLET AIR SYSTEM
The air filter housing mounted-heated inlet air sys­
tem is no longer used on any Dodge Truck gas pow­
ered engine.
EXHAUST GAS RECIRCULATION (EGR) SYSTEMS
GENERAL INFORMATION
The EGR system reduces oxides of nitrogen (NOx)
in the engine exhaust and helps prevent spark
knock. This is accomplished by allowing a predeter­
mined amount of hot exhaust gas to recirculate and
dilute the incoming fuel/air mixture. This dilution
reduces peak flame temperature during combustion.
The system consists of an intake manifold mounted
EGR valve (Fig. 1) and connecting hoses. The vac­
uum to the EGR is controlled by the electric EGR
transducer (EET) (Figs. 1 and 2). The EET is a dual
electric/vacuum function switch. It is controlled by
engine vacuum and the powertrain control module
(PCM).
Fig. 1 EGR System—Gas Powered Engines
EGR OPERATION
The electric exhaust gas recirculation transducer
(EET) is a back pressure transducer and an electric
vacuum solenoid combined into a single unit (Figs. 1
and 2). The vacuum solenoid portion of the EET re­
ceives its electrical signal from the powertrain con­
trol module (PCM). Using this signal, the solenoid
regulates the vacuum flowing through to the trans­
ducer portion of the EET. The back pressure trans-
page
Heated Inlet Air System . 10
Oxygen ( 0
2
) Sensor 13
ELECTRICAL VACUUM
CONNECTION SUPPLY
9125-34
Fig. 2 Electric EGR Transducer (EET)—Gas
Powered Engines
ducer measures the amount of exhaust gas back
pressure on the exhaust side of the EGR valve. It
then varies the strength of the vacuum signal ap­
plied to the EGR valve. The transducer uses this
back pressure signal to provide the correct amount of
exhaust gas recirculation under all conditions.
The vacuum supply for the EGR valve is controlled
by the EET. The electrical solenoid portion of the
EET is controlled by the powertrain control module
(PCM). The PCM monitors engine coolant tempera­
ture and other operating conditions to determine
when EGR operation is desired. Refer to Open Loop/
Closed Loop Modes of Operation in Group 14, Fuel
Systems for a description of EGR solenoid operation
based on engine operating conditions.
If the electrical connector to the EET is dis­
c o n n e c t e d or the electrical signal is lost, the
EGR valve will operate at all times. This results
in poor engine performance and reduced driveability
during certain operating conditions.
Vacuum flows between the solenoid portion of the
EET and the transducer portion of the EET. This
happens only when the solenoid is not electrically en­
ergized. The transducer is connected to the EGR
valve by a vacuum hose and a back pressure hose.
The transducer is controlled by exhaust back pres­
sure and is ported to the exhaust manifold through a
hose connecting it to the bottom of the EGR valve.
Vacuum will be supplied to the EGR valve and
EGR operation will begin when: