EXHAUST GAS RECIRCULATION
TABLE OF CONTENTS
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EXHAUST GAS RECIRCULATION
DESCRIPTION..........................3
OPERATION............................3
VA LV E
DESCRIPTION..........................3
OPERATION............................3REMOVAL.............................4
INSTALLATION..........................4
VALVE COOLER
DESCRIPTION..........................4
REMOVAL.............................4
INSTALLATION..........................5
EXHAUST GAS
RECIRCULATION
DESCRIPTION
The EGR system reduces oxides of nitrogen (NOx)
in the engine exhaust. This is accomplished by allow-
ing a predetermined amount of hot exhaust gas to
recirculate and dilute the incoming fuel/air mixture.
A malfunctioning EGR system can cause engine
stumble, sags, or hesitation, rough idle, engine stall-
ing and poor driveability.
OPERATION
The system consists of:
²An EGR valve assembly. The valve is located on
the rear of the engine above the exhaust manfiold.
²An EGR solenoid.The EGR solenoid controls the
ªon timeº of the EGR valve.
²The ECM operates the EGR solenoid. The ECM
is located inside the vehicle under the instrument
panel.
²An EGR tube connects a passage in the EGR
valve to the rear of the exhaust manifold.
²The vacuum pump supplies vacuum for the EGR
solenoid and the EGR valve. This pump also supplies
vacuum for operation of the power brake boosterb
and the heating and air conditioning system. The
pump is located internally in the front of the engine
block and is driven by the crankshaft gear.²Vacuum lines and hoses connect the various
components.
When the ECM supplies a variable ground signal
to the EGR solenoid, EGR system operation starts to
occur. The ECM will monitor and determine when to
supply and remove this variable ground signal. This
will depend on inputs from the engine coolant tem-
perature, throttle position and engine speed sensors.
When the variable ground signal is supplied to the
EGR solenoid, vacuum from the vacuum pump will
be allowed to pass through the EGR solenoid and on
to the EGR valve with a connecting hose.
Exhaust gas recirculation will begin in this order
when:
²The ECM determines that EGR system opera-
tion is necessary.
²The engine is running to operate the vacuum
pump.
²A variable ground signal is supplied to the EGR
solenoid.
²Variable vacuum passes through the EGR sole-
noid to the EGR valve.
²The inlet seat (poppet valve) at the bottom of
the EGR valve opens to dilute and recirculate
exhaust gas back into the intake manifold.
The EGR system will be shut down by the ECM
after 60 seconds of continuous engine idling to
improve idle quality.
RGEXHAUST GAS RECIRCULATION25a-3
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Generic Scan Tool Code DRB IIITScan Tool Display
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P0335 CKP Position Sensor Circuit Dynamic Plausibility
CKP Position Sensor Circuit Overspeed Recognition
CKP Position Sensor Circuit Static Plausibility
P0340 CMP Position Sensor Circuit CMP/CKP Sync. Failure
CMP Position Sensor Circuit Dynamic Plausibility
CMP Position Sensor Circuit Fuel Shut-Off Activated
CMP Position Sensor Circuit Signal Frequency Too High
CMP Position Sensor Circuit Static Plausibility
P0380 Glow Plug Circuit A Open Circuit
Glow Plug Circuit A Short Circuit
P0403 EGR Solenoid Circuit Open Circuit
EGR Solenoid Circuit Short Circuit
P0480 Fan 1 Control Circuit Open Circuit
Fan 1 Control Circuit Short Circuit
P0481 Fan 2 Control Circuit Open Circuit
Fan 2 Control Circuit Short Circuit
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Vehicle Speed Sensor Frequency High Level Duration
Vehicle Speed Sensor Plausibility
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P0514 Battery Temperature Sensor Circuit Signal Voltage Too High
P0520 Oil Pressure Sensor Circuit MALF Signal Voltage Too High
Oil Pressure Sensor Circuit MALF Signal Voltage Too Low
Oil Pressure Sensor Circuit MALF Signal Voltage Too Low or High
P0530 A/C Pressure Sensor Circuit Plausibility
A/C Pressure Sensor Circuit Signal Voltage Too High
A/C Pressure Sensor Circuit Signal Voltage Too Low
A/C Pressure Sensor Circuit Supply Voltage Too High Or Low
P0560 System Voltage Too High
System Voltage Too Low
P0579 Speed Control Switch Signal Circuit Voltage Too High
Speed Control Switch Signal Circuit Voltage Too Low
P0606 ECM Error Gate Array - Communication
ECM Error Gate Array - Communication Not Verified
ECM Error Gate Array - Quantity Stop
ECM Error Gate Array - Has Occurred
25a - 8 ON-BOARD DIAGNOSTICSRG
ON-BOARD DIAGNOSTICS (Continued)
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