Chrysler 1998 Voyager Service Manual page 1922

25 - 18 EMISSION CONTROL SYSTEMS
EXHAUST GAS RECIRCULATION (EGR) SYSTEM
DESCRIPTION AND OPERATION
GENERAL INFORMATION . . . . . . . . . . . . . . . . . 18
DIAGNOSIS AND TESTING
EGR GAS FLOW TEST . . . . . . . . . . . . . . . . . . . 20
EGR SYSTEM ON-BOARD DIAGNOSTICS . . . . . 19
EGR SYSTEM TEST . . . . . . . . . . . . . . . . . . . . . 19
EGR VALVE CONTROL (TRANSDUCER) TEST . 21
EGR VALVE LEAKAGE TEST . . . . . . . . . . . . . . . 20
DESCRIPTION AND OPERATION
GENERAL INFORMATION
Refer to Monitored Systems - EGR Monitor in this
group for more information.
The 3.0, 3.3, and 3.8L engines use Exhaust Gas
Recirculation (EGR) systems (Fig. 1) and (Fig. 2).
The EGR system reduces oxides of nitrogen (NOx) in
engine exhaust and helps prevent spark knock. The
system allows a predetermined amount of hot
exhaust gas to recirculate and dilute the incoming
air/fuel mixture. The diluted air/fuel mixture reduces
peak flame temperature during combustion.
The EGR system consists of:
• EGR tube (connects a passage in the intake
manifold to the exhaust manifold)
• EGR valve
• Electronic EGR Transducer
• Connecting hoses
Fig. 1 EGR Mounting—3.0L Engine
The Electronic EGR Transducer contains an elec-
trically operated solenoid and a back-pressure trans-
INDEX
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REMOVAL AND INSTALLATION
EGR TUBE SERVICE—3.0L ENGINES . . . . . . . . 22
EGR TUBE SERVICE—3.3/3.8L ENGINES . . . . . 22
EGR VALVE SERVICE—3.0L ENGINES . . . . . . . 21
EGR VALVE SERVICE—3.3/3.8L ENGINES . . . . 22
SPECIAL TOOLS
EMISSION CONTROL SYSTEM . . . . . . . . . . . . . 23
Fig. 2 EGR Mounting—3.3/3.8L Engines
ducer (Fig. 3). The PCM operates the solenoid. The
PCM determines when to energize the solenoid.
Exhaust system back-pressure controls the trans-
ducer.
When the PCM energizes the solenoid, vacuum
does not reach the transducer. Vacuum flows to the
transducer when the PCM de-energizes the solenoid.
When exhaust system back-pressure becomes high
enough, it fully closes a bleed valve in the trans-
ducer. When the PCM de-energizes the solenoid and
back-pressure closes the transducer bleed valve, vac-
uum flows through the transducer to operate the
EGR valve.
De-energizing the solenoid, but not fully closing the
transducer bleed hole (because of low back-pressure),
varies the strength of vacuum applied to the EGR
valve. Varying the strength of the vacuum changes
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