Daewoo CIELO EURO III Manual page 487

EXHAUST GAS RECIRCULATION (EGR) PINTLE POSITION SENSOR HIGH
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 Ignition voltage is between 11.7 and 16 volts.
1.5L SOHC
D EGR position is greater than 98%.
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.
D A history Diagnostic Trouble Code (DTC) is stored.
D EGR is disabled.
DAEWOO T-154 BL2,3
DIAGNOSTIC TROUBLE CODE (DTC) P0406
VOLTAGE
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.
3. If the EGR valve 5 volt reference is shorted to
ground, the Digital Voltmeter (DVM) will read no
voltage and additional DTCs may be set and the en-
gine performance will be poor. When this circuit is
open, only a DTC P0405 will be set.
4. Jumpering the 5 volt reference circuit to the signal
circuit checks the signal circuit and the ECM.
The scan tool should display the Actual EGR Posi-
tion as 100% if the signal circuit and ECM are
OK.
6. Although the ECM and circuitry acted correctly
in the previous step, a problem may still lie within the
terminals which would not show up in probe type
testing. Be sure to check the terminals for being
backed out, improperly formed or damaged, and for
poor tension.
10. 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
ENGINE CONTROLS 1F – 317