filter DAEWOO NUBIRA 2004 Service Owner's Manual

ENGINE CONTROLS 1F – 373
DAEWOO V–121 BL4
Conditions for Clearing the MIL/DTC
S The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S The DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
S Fuel pressure – The system will be lean if the fuel
pressure is too low. It may be necessary to monitor
the fuel pressure while driving the vehicle at various
road speeds and/or loads to confirm. Refer to ”Fuel
System Diagnosis” in this section.
S Manifold Absolute Pressure (MAP) sensor – An
output that causes the ECM to sense a lower than
normal manifold pressure (high vacuum) can cause
the system to go lean. Disconnecting the MAP sen-
sor will allow the ECM to substitute a fixed (default)
value for the MAP sensor. If the lean condition is
gone when the sensor is disconnected, substitute a
known good sensor and recheck.
S Fuel contamination – Water, in even small amounts
near the in–tank fuel pump inlet can be delivered to
the injector. The water causes a lean exhaust and
can set DTC P0131.
S Sensor harness – The HO2S1 sensor pigtail may
be mis–positioned and contacting the exhaust man-
ifold.
S Engine misfire – A misfiring cylinder will result in
unburned oxygen in the exhaust, which could cause
DTC P0131 to set. Refer to DTC P0300 Engine
Misfire in this section.S Cracked Front Heated Oxygen Sensor – A cracked
HO2S1 or poor ground at the sensor could cause
DTC P0131. Refer to”Symptoms Diagnosis” in this
section.
S Plugged fuel filter – A plugged fuel filter can cause
a lean condition and cause a DTC P0131 to set.
S Plugged Front Heated Oxygen Sensor – A plugged
reference port on the HO2S1 will indicate a lower–
than–normal voltage output from the HO2S1.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic 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. This step determines if DTC P0131 is the result of
a hard failure or an intermittent condition. It may be
necessary to operate the vehicle within the Freeze
Frame conditions and Conditions for Setting the
DTC in order to duplicate the malfunction detected
by the ECM.
4. This step simulates DTC P0134. If the ECM senses
the change, the ECM and the wiring are OK.
6. The replacement ECM must be reprogrammed.
Refer to the latest Techline procedure for ECM re-
programming.
8. If no malfunctions have been found at this point and
no additional DTCs were set, refer to ”Diagnostic
Aids” for additional checks and information.
DTC P0131 – Front Heated Oxygen Sensor (HO2S1) Low Voltage
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) System
Check.
Is the check completed?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Install a scan tool to the Data Link Connector
(DLC).
2. Start the engine and idle at normal operating
temperature.
Does the Front Heated Oxygen Sensor (HO2S1)
voltage remain below the value specified?0.1 VGo to Step 4Go to Step 3
31. Review the Freeze Frame data and note the
parameters.
2. Operate the vehicle within the Freeze frame
conditions and Conditions For Setting the DTC
as noted.
Does the HO2S1 voltage stay below the specified
value?0.1 VGo to Step 4Go to Step 7

ENGINE CONTROLS 1F – 385
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0135
FRONT HEATED OXYGEN SENSOR (HO2S1) HEATER
CIRCUIT NOT FUNCTIONING
Circuit Description
Heated oxygen sensors (HO2S) are used for fuel control
and post catalyst monitoring. Each HO2S compares the
oxygen content of the surrounding air with the oxygen con-
tent in the exhaust stream. The HO2S must reach operat-
ing temperature to provide an accurate voltage signal. A
heating element inside the HO2S minmizes the time re-
quired for the sensor to reach operating temperature. Volt-
age is provided to the heater by the ignition 1 voltage cir-
cuit through a fuse. With the engine running, ground is
provided to the heater by the HO2S heater low control cir-
cuit, through a low side driver within the engine control
module (ECM). The ECM monitors the current flow
through the heater for diagnosis.
If the ECM detects that the HO2S heater current is above
or blelow a specified range, DTC P0135 seats.
Conditions for Setting the DTC
S DTCs P0106, P0117, P0118, P1017 are not set.
S Engine run time is greater than 200 seconds.
S Filtered O2 heater current is less than 0.025 amps.
Action Taken When the DTC SetsS The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive ignition cycle with a fail.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history Diagnostic Trouble Code (DTC) is stored.
Conditions for Clearing the MIL/DTC
S The MIL will turn off after three consecutive ignition
cycles in which the diagnostic runs without a fault.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
An intermittent may be caused by rubbed through wire in-
sulation or a wire contacting the exhaust.
Check for poor connection or damaged harness – inspect
harness connectors for the following conditions:
S Improper mating
S Broken locks
S Improperly formed
S Damaged terminals
S Poor terminal–to–wire connection

1F – 404IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0172
FUEL TRIM SYSTEM TOO RICH
System Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a Closed Loop air/fuel
metering system is used. While in Closed Loop, the En-
gine Control Module (ECM) monitors the Front Heated
Oxygen Sensor (HO2S1) signal voltage and adjusts fuel
delivery based on signal voltage. A change made to fuel
delivery will be indicated by the long and short term fuel
trim values which can be monitored with the scan tool.
Ideal fuel trim values are around 128 (0%). If the HO2S1
signal is indicating a lean condition, the ECM will add fuel
resulting in fuel trim values above 128 (0% to 100%). If a
rich condition is detected, the fuel trim values will be below
128 (0% to –100%), indicating that the ECM is reducing
the amount of fuel delivered. If exhaust emissions reach
an excessive level due to a lean or rich condition, a fuel
trim Diagnostic Trouble Code (DTC) is set.
Conditions for Setting the DTC
S The average of adaptive index multiplier value is
less than 0.75.
S No intrusive tests active.
S DTCs P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0131, P0132,
P0133, P0134, P0135, P1167, P1171, P0336,
P0337, P0341, P0342, P0402, P0404, P1404,
P0405, P0406, P0443, P0506, and P0507 are not
set.
S Throttle Position (TP) is less than 95%.
S Engine speed is between 700 and 6000 rpm.
S Barometric Pressure (BARO) is greater than 72.0
kPa (10.4 psi).
S Coolant temperature is between 70°C (158°F) and
11 5°C (239°F).
S Manifold Absolute Pressure (MAP) is between 25
kPa (3.6 psi) and 99.7 kPa (14.5 psi).
S Intake Air Temperature (IAT) is between –40°C
(–40°F) and 120°C (248°F).
S Airflow is between 1.5 and 45 g/sec.
S Vehicle speed is less than 140 km/h (87 mph).
S System is in closed loop.
S Adaptive index is ready.
S System voltage is greater than 11 volts.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after two consecutive ignitions cycle in which the
diagnostic runs with the fault active (SOHC).
S The Malfunction Indicator Lamp (MIL) will illuminate
after first consecutive ignitions cycle (DOHC).
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.Conditions for Clearing the MIL/DTC
S The MIL will turn off after two consecutive ignition
cycles in which the diagnostic runs without a fault
within the freeze frame conditions that the DTC
failed.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S The DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Important : After repairs, use the scan tool Fuel Trim Re-
set function to reset the long–term fuel trim to 128 (0%).
Check for poor connection at the ECM. Inspect the har-
ness connectors for the following conditions:
S Backed–out terminals.
S Improper mating.
S Broken locks.
S Improperly formed.
S Damaged terminals.
S Poor terminal–to–wire connection.
Inspect the wiring harness for damage. If the harness ap-
pears to be OK, observe the HO2S1 display on the scan
tool while moving the connectors and the wiring harness
related to the engine harness. A change in the display will
indicate the location of the fault.
If a DTC P1404 is also set, check the 5 volt reference cir-
cuits for a short to voltage.
Check for a restricted exhaust system.
A shorted 5 volt reference circuit may cause a DTC P0172
to set. Check the 5 volt reference sensors for abnormal
readings.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic 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.
5. A clogged air cleaner filter element restricts the air-
flow coming into the engine. This step checks the
condition of the air cleaner filter.
17. A leaky injector can cause a rich condition and set
DTC P0172. Refer to ”Fuel Injector Balance Test”
in this section.
19. A loose TP sensor may not set a TP sensor related
DTC, but may cause the system to become rich by
a higher–than–actual TP reading.

ENGINE CONTROLS 1F – 405
DAEWOO V–121 BL4
DTC P0172 – Fuel Trim System Too Rich
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) System
Check.
Was the check performed?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Install the scan tool to the Data Link Connector
(DLC).
2. Turn the ignition ON.
Are any component related Diagnostic Trouble
Codes (DTCs) set?–Go to applica-
ble DTC tableGo to Step 3
3With the engine running, operate the vehicle until the
LOOP STATUS indicates closed.
Is the Long Term Fuel Trim value above the specified
value?–20%Go to Step 4Go to Step 5
41. Turn the ignition switch ON, with the engine
OFF.
2. Review the Freeze Frame data and note the
parameters.
3. Operate the vehicle within the Freeze Frame
conditions and Conditions for Setting The DTC
as noted.
Does the Long Term Fuel Trim value above the spe-
cified value while operating under the specified con-
ditions?–20%Go to Step 21Go to Step 5
5Visually/physically check the air cleaner filter for ex-
cessive dirt or being plugged and repair as needed.
Is the repair complete?–Go to Step 21Go to Step 6
6Visually/physically check the air intake system for
collapsed or restricted and repair as needed.
Is the repair complete?–Go to Step 21Go to Step 7
7Inspect the throttle body inlet for damaged or foreign
objects which may partially block the airflow and re-
pair as needed.
Is the repair complete?–Go to Step 21Go to Step 8
81. Turn the ignition OFF.
2. Inspect the throttle bore, throttle plate and Idle
Air Control (IAC) passages for clocking and
foreign objects and repair as needed.
Is the repair complete?–Go to Step 21Go to Step 9
9Start the engine with the vehicle in park or neutral
and A/C off and note the idle quality.
Is a low or unsteady idle being experienced?–Go to Step 10Go to Step 12
10Idle the engine.
Are the IAC counts below the specified value?100Go to Step 12Go to Step 11

ENGINE CONTROLS 1F – 447
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0325
KNOCK SENSOR INTERNAL MALFUNCTION
System Description
The Knock Sensor (KS) system is used to detect engine
detonation, allowing the Engine Control Module (ECM) to
retard the ignition control spark timing based on the KS
signal being received. The KS produces an AC signal so
that under a no–knock condition the signal on the KS cir-
cuit measures about 0.007 volts AC. The KS signal’s am-
plitude and frequency depend upon the amount of knock
being experienced. The ECM contains a nonreplaceable
knock filter module called a Digitally Controlled Signal–to–
Noise Enhancement Filter (DSNEF) module. This filter
module in the ECM determines whether or not knock is oc-
curring by comparing the signal level on the KS circuit with
the voltage level on the noise channel. The noise channel
allows the ECM to reject any false knock signal by knowing
the amount of normal engine mechanical noise present.
Normal engine noise varies depending on engine speed
and load. When the ECM determines that an abnormally
low noise channel voltage level is being experienced,
Diagnostic Trouble Code (DTC) P0325 will set.
Conditions for Setting the DTC
S DSNEF A/D reading is less than 1.0% or greater
than 80% any of the 4 cylinders.
S Vacuum is less than the predetermined value (10 to
50 kPa, based on rpm).
S The rpm is greater than 1600.
S DTC(s) P0106, P0107, P0108 are not set.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will not illumi-
nate.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Failure Records buffers.
S A history DTC is stored.
Conditions for Clearing the MIL/DTCS A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
Check and correct any abnormal engine noise before us-
ing the diagnostic table.
Any circuitry, that is suspected as causing the complaint,
should be thoroughly checked for the following conditions:
S Backed–out terminals
S Improper mating
S Broken locks
S Improperly formed
S Damaged terminals
S Poor terminal–to–wire connection
S Physical damage to the wiring harness
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic 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. If the conditions for the test as described above are
met, a DTC P0325 will set and MIL will illuminate.
4. If the engine has an internal knock or audible noise
that causes a knocking type noise on the engine
block, the knock sensor may be responding to the
noise.
6. The replacement ECM must be reprogrammed.
Refer to the latest Techline procedure for ECM re-
programming.
DTC P0325 – Knock Sensor Internal Malfunction
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) System
Check.
Was the check performed?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Install a scan tool to the Data Link Connector
(DLC).
2. Clear the Diagnostic Trouble Codes (DTCs).
3. Start the engine.
4. Operate the vehicle within the Conditions for
Setting the DTC as noted.
Is the DTC set again.–Go to Step 3Go to Step 6

1F – 468IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0401
EXHAUST GAS RECIRCULATION INSUFFICIENT FLOW
Circuit Description
An Exhaust Gas Recirculation (EGR) system is used to
lower Nitrogen Oxide (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 diluted
with the exhaust gases, combustion temperatures are re-
duced
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 an En-
gine Control Module (ECM) controlled pintle. The ECM
controls the pintle position using inputs from the Throttle
Position (TP) and Manifold Absolute Pressure (MAP) sen-
sors. The ECM then commands the EGR valve to operate
when necessary by controlling an ignition signal through
the ECM. This can be monitored on a scan tool as the De-
sired 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 representing the
EGR valve pintle position is sent to the ECM. This feed-
back 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 will determine if there is a reduction in EGR
flow.
Conditions for Setting the DTC
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0201, P0202, P0203, P0204,
P0351, P0352, P0402, P0404, P1404, P0405,
P0406 and P0502 are not set.
S Test in Decel Fuel Cutoff (DFCO) mode.
S Barometric Pressure (BARO) is greater than 72
kPa (10.4 psi).
S Vehicle speed is greater than 18 km/h (11.2
mph).
S A/C clutch/transmission clutch are unchanged.
S Rpm is between 1400 and 3000 for manual
transaxle.
S Rpm is between 1300 and 2900 for automatic
transaxle.
S Compensated MAP is with 10.3 to 32 kpa (1.5 to
4.6 psi) range.
S Start test
S Throttle position (TP) sensor is less then 1%.
S EGR is less than 1%.
S Change in MAP is less than 1.0 kpa (0.15 psi)Note : Test will be aborted when:
S Change in vehicle speed is greater than 5km/h (3.1
mph).
S Rpm is increased more than 75.
S EGR opened less than 90% commanded position.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will not illumi-
nate.
S The ECM will store conditions which were present
when the DTC set as Failure Records data only.
This information will not be stored in the Freeze
Frame data.
S A history Diagnostic Trouble Code (DTC) is stored.
S EGR is disabled.
Conditions for Clearing the MIL/DTC
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
The EGR Decel Filter value can be a great aid in determin-
ing if a problem exists and to verify repairs. The EGR De-
cel Filter is an average of the difference in the expected
MAP change and the actual MAP change caused by open-
ing the EGR valve during a deceleration, and is used to de-
termine when the MIL is illuminated. By driving the vehicle
up to approximately 97 km/h (60 mph) and decelerating to
32 km/h (20 mph), it can be determined if the EGR system
is OK, partially restricted, or fully restricted.
A more negative number (less than –3) indicates that the
system is working normally, whereas a positive number in-
dicates that the system is being restricted and that the ex-
pected amount of EGR flow is was not seen. A number
that falls between negative 3 and positive 2 indicates that
the system is partially restricted but not restricted enough
to cause an emissions impact.
The EGR Decel Filter value should always be at –3 or low-
er. If the EGR Decel Filter number becomes more positive
(towards 0 or more), then the EGR system is becoming re-
stricted. Look for possible damage to the EGR pipe or for
a restriction caused by carbon deposits in the EGR pas-
sages or on the EGR valve.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic 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

ENGINE CONTROLS 1F – 469
DAEWOO V–121 BL4
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 is totally restricted or par-
tially restricted.
3. Visually and physically inspect the EGR passages
and valve for excessive carbon deposits or dam-
age.
4. Be sure all gasket material is removed from the
EGR mounting surface. Even a small amount of
material may cause a DTC P0401 to set.
5. This step verifies if the fault is present and also ver-
ifies if a repair corrected the problem. If the EGR
Deceleration Filter value stays near 0 or a positivenumber after several tests have been run, then a
small restriction may still exist. Be sure to check the
EGR pipe for damage or dents and the EGR valve
for any excessive carbon build up. Only 1 test per
ignition cycle will run unless a DTC P0401 has
been cleared or the battery has been disconnected.
6. Clearing DTCs is a very important step for this
diagnostic. The clearing function allows the EGR
valve to relearn a new pintle position as the old
pintle position was inaccurate due to the failure that
caused the DTC. The DTC must be cleared with
the ignition ON, engine OFF or when the engine is
idling. If the ECM sees a EGR command, the new
pintle will not be learned.
DTC P0401 – Exhaust Gas Recirculation Insufficient Flow
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) System
Check.
Was the check performed?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Install a scan tool to the Data Link Connector
(DLC).
2. Start the engine and allow the engine to idle.
3. Command the Exhaust Gas Recirculation
(EGR) valve to the specific value.
Does the engine stall or attempt to stall?50%Go to Step 5Go to Step 3
31. Turn the ignition OFF.
2. Disconnect the EGR valve connector and re-
move the EGR valve.
3. Inspect the EGR valve passages and pipe for a
restriction or damages and repair as needed.
Is the repair complete?–Go to Step 5Go to Step 4
4Replace the EGR valve.
Is the repair complete?–Go to Step 5–
51. Disconnect the battery for more than 10 sec-
onds.
2. Drive the vehicle up to 97 km/h (60mph)
3. Release the throttle and allow the vehicle to
decelerate to 32 km/h (20mph).
Is the EGR Decel Filter value greater than specified
value?0Go to Step 3Go to Step 6
61. Using the scan tool, clear the Diagnostic
Trouble Codes (DTCs).
2. Start the engine and idle at normal operating
temperature.
3. Operate the vehicle within the Conditions for
setting this DTC as specified in the supporting
text.
Does the scan tool indicate that this diagnostic has
run and passed?–Go to Step 7Go to Step 2
7Check if any additional DTCs are set.
Are any DTCs displayed that have not been diag-
nosed?–Go to
Applicable DTC
tableSystem OK

ENGINE CONTROLS 1F – 471
DAEWOO V–121 BL4
The EGR Decel Filter value should always be at –3 or low-
er. If the EGR Decel Filter number becomes more positive
(towards 0 or more), then the EGR system is becoming re-
stricted. Look for possible damage to the EGR pipe or for
a restriction caused by carbon deposits in the EGR pas-
sages or on the EGR valve.
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic 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 dif-
ference between the current and commanded posi-
tion 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 dis-
played on the DVM to change after the scan tool
commands the EGR valve to operate.
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 pre-
vious step if the EGR control circuit was shorted to
B+ and the Actual EGR Position on the scan toolwill display 100%. A test light that did not illuminate,
indicates that the circuit may be open or shorted to
ground.
9. If the EGR valve 5 volt reference is shorted to volt-
age, the digital voltmeter (DVM) will read battery
voltage and additional DTCs may be set and the
engine performance will be poor.
12. The replacement ECM must be reprogrammed.
Refer to the latest Techline procedure for ECM re-
programming.
13. Although the circuitry acted correctly when
checked, 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 ten-
sion.
17. 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 small amount of material may cause a DTC
P0401 to set.
18. Check the terminals for being backed out, improp-
erly formed or damaged, and for poor tension.
19. Clearing DTCs is a very important step for this
diagnostic. The clearing function allows the EGR
valve to relearn a new pintle position as the old
pintle position was inaccurate due to the failure that
caused the DTC. The DTC must be cleared with
the ignition ON, engine OFF or when the engine is
idling. If the ECM sees a EGR command, the new
pintle will not be learned.
20. If no malfunctions have been found at this point and
no additional DTCs were set, refer to ”Diagnostic
Aids” in this section for additional checks and infor-
mation.
DTC P0402 – Exhaust Gas Recirculation Excessive Flow
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) System
Check.
Was the check performed?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
21. Install a scan tool to the Data link Connector
(DLC).
2. Turn the ignition ON.
3. Command the Exhaust Gas Recirculation
(EGR) valve to the specific values.
Does the Actual EGR Position follow the Desired
EGR Position?25%, 50%,
75%, 100%Go to Step 19Go to Step 3
31. Turn the ignition OFF.
2. Disconnect the EGR valve.
3. Turn the ignition ON.
4. With a test light connected to B+, probe the
EGR valve wiring harness connector terminal
2.
Does the test light illuminate?–Go to Step 4Go to Step 5

1F – 548IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P1171
FUEL TRIM SYSTEM LEAN DURING POWER
ENRICHMENT
System Description
The internal circuitry of the Engine control Module (ECM)
can identify if the vehicle fuel system is capable of supply-
ing adequate amounts of fuel during heavy acceleration(
power enrichment). When a Power Enrichment (PE)
mode of operation is requested by heavy acceleration dur-
ing Closed Loop operation, the ECM will provide more fuel
to the engine. Under these conditions the ECM should de-
tect a rich condition. If this reich condition is nor detected
at this time, Diagnostic Trouble Code (DTC) P1171 will set.
A plugged fuel filter or restricted fuel line can prevent ade-
quate amount of fuel from being supplied during Power
Enrichment mode.
Conditions for Setting the DTC
S HO2S1 voltage is less than 0.35 volts in Power En-
richment (PE) mode.
S Engine is operating in Closed Loop and in PE
mode.
S Engine Coolant Temperature (ECT) is greater than
60°C (140°F).
S System voltage is greater than 10 volts.
S Air/Fuel ration is less than 13.5:1.
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0171, P0172, P0201, P0202,
P0203, P0204, P0300, P0336, P0337, P0351,
P0352, P0402, P0404, P0405, P0406, P0506,
P0507, P1404, and P0443 are not set.
S 3 second delay after in PE mode.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after two consecutive ignition cycle with a fail.
S The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records
buffers.
S A history DTC is stored.
S The vehicle will operate in Open Loop.Conditions for Clearing the MIL/DTC
S The MIL will turn off after three consecutive ignition
cycles in which the diagnostic runs without a fault.
S A history DTC will clear after 40 consecutive warm–
up cycles without a fault.
S DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.v
Diagnostic Aids
A restricted fuel filter can supply adequate amounts of fuel
at idle, but may not be able to supply enough fuel during
heavy acceleration.
Water or alcohol n fuel may cause low HO2S1 voltage dur-
ing acceleration.
Check for adequate amount of fuel in the Tank.
When the engine is idling or at steady cruise, the HO2S1
voltage should vary from between approximately a00 to
900 millivolts. During power enrichment mode, more fuel
is needed, and the HO2S1 should rise above 444 milli-
volts.
Check for faulty or plugged injector(s).
Test Description
Number(s) below refer to the step number(s) on the Diag-
nostic 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.
4. This step checks to see if the HO2S1 is operating
properly.
6. If no faults have been found at this point and no
additional DTCs were set, refer to ”Diagnostic Aids”
in this section for additional checks and informa-
tion.

ENGINE CONTROLS 1F – 579
DAEWOO V–121 BL4
SURGES OR CHUGGLES
Definition : Engine power varies under steady throttle or
cruise, making it feel as if the vehicle speeds up and slows
down with no change in the accelerator pedal position.
Important : Make sure the driver understands Torque
Converter Clutch (TCC) and A/C compressor operation as
described in the owner’s manualThe speedometer reading and the speed reading on the
scan tool should be equal.
Before diagnosing the symptom, check service bulletins
for updates.
Step
ActionValue(s)YesNo
1Were the Important Preliminary Checks performed?–Go toStep 2Go to
”Important Pre-
liminary
Checks”
2Connect the scan tool to the Data Link Connector
(DLC).
Does the Front Heated Oxygen Sensor (HO2S1) re-
spond quickly to different throttle positions?–Go toStep 4Go toStep 3
31. Check the HO2S1 sensor for silicone or other
contaminants from fuel or use of improper
Room Temperature Vulcanizing (RTV) sealant.
2. Replace the contaminated HO2S1 sensor.
Is the repair complete?–System OK–
41. Drive the vehicle at the speed of the complaint.
2. Monitor the long term fuel trim reading using
the scan tool.
Is the long term fuel trim reading within the value
specified?–20–25%Go toStep 7Go toStep 5
5Is the long term fuel trim reading below the value
specified?–20%Go to
”Diagnostic
Aids for DTC
P0172”Go toStep 6
6Is the long term fuel trim reading above the value
specified?25%Go to
”Diagnostic
Aids for DTC
P0171”–
7Check the fuel system pressure while the condition
exists.
Is the fuel system pressure within specifications?41–47 psi
(284–325 kPa)Go toStep 8Go toStep 17
8Check the in–line fuel filter.
Is the filter dirty or plugged?–Go toStep 18Go toStep 9
9Perform an injector diagnosis.
Does the injector balance test pinpoint the problem?–Go toStep 19Go toStep 10
101. Check for proper ignition voltage output using a
spark tester.
2. Inspect the spark plugs for cracks, wear, im-
proper gap, burned electrodes, or heavy de-
posits.
Is the problem found?–Go toStep 11Go toStep 12
11Repair or replace any ignition system components
as needed.
Is the repair complete?–System OK–