Daewoo CIELO EURO III Manual page 475

EXHAUST GAS RECIRCULATION (EGR) OPENED
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Oxides of Nitrogen (NOx) emission levels caused
by high combustion temperatures. It accomplishes this
by feeding small amounts of exhaust gases back into
the combustion chamber. When the air/fuel mixture is di-
luted with the exhaust gases, combustion temperatures
are reduced.
A linear EGR valve is used on this system. The linear
EGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold through an
orifice with a engine
control module (ECM) controlled pintle. The ECM
controls the pintle position using inputs from the Throttle
Position (TP) and Manifold Absolute Pressure (MAP)
sensors. The ECM then commands the EGR
valve to operate when necessary by controlling an igni-
tion signal through the ECM. This can be moni-
tored on a scan tool as the Desired EGR Position.
The ECM monitors the results of its command
through a feedback signal. By sending a 5 volt reference
and a ground to the EGR valve, a voltage signal repre-
senting the EGR valve pintle position is sent to the
ECM. This feedback signal can also be monitored on a
scan tool and is the actual position of the EGR pintle.
The Actual EGR Position should always be near the
commanded or Desired EGR Position.
This Diagnostic Trouble Code (DTC) will detect an open
valve position.
Conditions for Setting the DTC
D Ignition voltage is between 11.7 volts and 16 volts.
D Desired EGR position is greater than 0.
D Engine is running.
D Difference between current and commanded position
is greater than 15%.
1.5L SOHC
D The change of desired EGR position is less than 3%.
D The air temperature is greater than 3_C (37.4_F).
D DTCs P0112, P0113, P0405, P0406 and P0502 are
not set.
.
Action Taken When the DTC Sets
D The Malfunction Indicator Lamp (MIL) will illuminate
after three (1.5L SOHC)
consecutive trip with a fail.
D The ECM will record operating conditions at the
time the diagnostic fails. This information will be
DAEWOO T-154 BL2,3
DIAGNOSTIC TROUBLE CODE (DTC) P0404
ENGINE CONTROLS 1F – 305
stored in the Freeze Frame and Failure Records buff-
ers.
D A history DTC is stored.
D EGR is disabled.
Conditions for Clearing the MIL/DTC
D The MIL will turn off after three (four –
1.5L SOHC) consecutive ignition cycles in which the
diagnostic runs without a fault.
D A history DTC will clear after 40 consecutive warm up
cycles without a fault.
D DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EGR and Desired EGR Posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the freeze frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic Table.
1. The On-Board Diagnostic (EOBD) System Check
prompts the technician to complete some basic
checks and store the freeze frame and failure re-
cords data on the scan tool if applicable. This
creates an electronic copy of the data taken when
the malfunction occurred. The information is then
stored on the scan tool for later reference.
2. Commanding the EGR valve open determines
whether the EGR system can control the EGR valve
accurately and if the fault is present. The difference
between the current and commanded position is
greater than 15%.
3. When the EGR valve electrical connector is discon-
nected, the scan tool should display the Actual EGR
Position as 0%. If it does not, the fault lies either in
the EGR signal circuit or the ECM.
4. There may be a slight delay for the voltage displayed
on the DVM to change after the scan commands the
EGR valve to operate. This time the engine must be
runned (1.5L SOHC only).
5. An open or poor connection condition may have
caused this DTC to set. Be sure to check the termi-
nals for being backed out, improperly formed or
damaged, and for poor tension.
7. The test light will have glowed brightly in the previous
step if the EGR control circuit was shorted to B+, and
the Actual EGR Position on the scan tool will display