Daewoo CIELO EURO III Manual page 479

EXHAUST GAS RECIRCULATION (EGR) CLOSED
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.
Conditions for Setting the DTC
D Engine running.
D Ignition voltage is between 11.7 and 16 volts.
D Desired EGR position is equal to 0.
1.5L SOHC
D Intake air temperature is greater than 3_C (37.4_F).
D DTCs P0112, P0113, P0405, P0406 and P0502 are
not set.
D Difference between current and learned low position
is greater than 6.29%.
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
stored in the Freeze Frame and Failure Records buff-
ers.
DAEWOO T-154 BL2,3
DIAGNOSTIC TROUBLE CODE (DTC) P1404
ENGINE CONTROLS 1F – 309
D A history Diagnostic Trouble Code (DTC) is stored.
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. 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 Positions on a cold
vehicle with a scan tool, the fault can be easily verified.
Check the freeze frame data to determine if the DTC set
when the vehicle was cold by viewing the Engine Cool-
ant 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.
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.
5. If the ERG valve 5 volt reference is shorted to volt-
age, the Digital Voltmeter (DVM) will read battery
voltage and additional DTCs may be set and engine
performance will be poor.
6. The replacement ECM must be repro-
grammed. Refer to the latest Techline procedure for
ECM reprogramming.
10. 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.
11. All circuits to the EGR valve are OK at this point.
The fault lies internally in the EGR valve and there-
fore must be replaced. Be sure all gasket material is
removed from the EGR mounting surface. Even a