fuel pressure DAEWOO NUBIRA 2004 Service Service Manual

1F – 110IENGINE CONTROLS
DAEWOO V–121 BL4
FUEL INJECTOR BALANCE TEST
A fuel injector tester is used to energize the injector for a
precise amount of time, thus spraying a measured amount
of fuel into the intake manifold. This causes a drop in the
fuel rail pressure that can be recorded and used tocompare each of the fuel injectors. All of the fuel injectors
should have the same pressure drop.
Fuel Injector Balance Test Example
Cylinder1234
First Reading296 kPa (43 psi)296 kPa (43 psi)296 kPa (43 psi)296 kPa (43 psi)
Second Reading131 kPa (19 psi)117 kPa (17 psi)124 kPa (18 psi)145 kPa (21 psi)
Amount Of Drop165 kPa (24 psi)179 kPa (26 psi)172 kPa (25 psi)151 kPa (22 psi)
Average Range:
156~176 kPa
(22.5~25.5 psi)Injector OKFaulty Injector – Too
Much Pressure DropInjector OKFaulty Injector – Too
Little Pressure Drop
CAUTION : The fuel system is under pressure. To
avoid fuel spillage and the risk of personal injury or
fire, it is necessary to relieve the fuel system pressure
before disconnecting the fuel lines.
CAUTION : Do not pinch or restrict nylon fuel lines.
Damage to the lines could cause a fuel leak, resulting
in possible fire or personal injury.
Notice : In order to prevent flooding of the engine, do not
perform the Injector Balance Test more than once (includ-
ing any retest on faulty fuel injectors) without running the
engine.
Test
1. Turn the ignition switch to ON in order to get the
fuel pressure to its maximum level.
2. Allow the fuel pressure to stabilize and then record
this initial pressure reading. Wait until there is no
movement of the needle on the fuel pressure
gauge.
3. Follow the manufacturer’s instructions for the use
of the adapter harness. Energize the fuel injector
tester once and note the fuel pressure drop at its
lowest point. Record this second reading. Subtract
it from the first reading to determine the amount of
the fuel pressure drop.
4. Disconnect the fuel injector tester from the fuel in-
jector.
5. After turning the ignition switch to ON, in order toobtain maximum pressure once again, make a con-
nection at the next fuel injector. Energize the fuel
injector tester and record the fuel pressure reading.
Repeat this procedure for all the injectors.
6. Retest any of the fuel injectors that the pressure
drop exceeds the 10 kPa (1.5 psi) of the average
pressure drop value.
7. Replace any of the fuel injectors that fail the retest.
8. If the pressure drop of all of the fuel injectors is
within 10 kPa (1.5 psi) of the average pressure
drop value, then the fuel injectors are flowing nor-
mally and no replacement should be necessary.
9. Reconnect the fuel injector harness and review the
symptom diagnostic tables.
10. An engine cool down period of 10 minutes is neces-
sary in order to avoid irregular readings due to hot
soak fuel boiling.
11. Connect the fuel pressure gauge carefully to avoid
any fuel spillage.
12. The fuel pump should run about 2 seconds after the
ignition is turned to the ON position.
13. Insert a clear tube attached to the vent valve of the
fuel pressure gauge into a suitable container.
14. Bleed the air from the fuel pressure gauge and
hose until all of the air is bled from the fuel pressure
gauge.
15. The ignition switch must be in the OFF position at
least 10 seconds in order to complete the Engine
Control Module (ECM) shutdown cycle.

ENGINE CONTROLS 1F – 111
DAEWOO V–121 BL4
TROUBLE CODE DIAGNOSIS
(1.4L/1.6L DOHC)
CLEARING TROUBLE CODES
Notice : To prevent Engine Control Module (ECM) dam-
age, the key must be OFF when disconnecting or recon-
necting the power to the ECM (for example battery cable,
ECM pigtail connector, ECM fuse, jumper cables,
etc.).When the ECM sets a Diagnostic Trouble Code
(DTC), the Malfunction Indicator Lamp (MIL) lamp will be
turned on only for type A, B and E but a DTC will be stored
in the ECM’s memory for all types of DTC. If the problemis intermittent, the MIL will go out after 10 seconds if the
fault is no longer present. The DTC will stay in the ECM’s
memory until cleared by scan tool. Removing battery volt-
age for 10 seconds will clear some stored DTCs.
DTCs should be cleared after repairs have been com-
pleted. Some diagnostic tables will tell you to clear the
codes before using the chart. This allows the ECM to set
the DTC while going through the chart, which will help to
find the cause of the problem more quickly.
DIAGNOSTIC TROUBLE CODES (1.4L/1.6L DOHC)
DTCFunctionError
TypeIlluminate MIL
P0107Manifold Absolute Pressure Sensor Low VoltageAYES
P0108Manifold Absolute Pressure Sensor High VoltageAYES
P0112Intake Air Temperature Sensor Low VoltageEYES
P0113Intake Air Temperature Sensor High VoltageEYES
P0117Engine Coolant Temperature Sensor Low VoltageAYES
P0118Engine Coolant Temperature Sensor High VoltageAYES
P0122Throttle Position Sensor Low VoltageAYES
P0123Throttle Position Sensor High VoltageAYES
P0131Front Heated Oxygen Sensor Low VoltageAYES
P0132Front Heated Oxygen Sensor High VoltageAYES
P0133Front Heated Oxygen Sensor No ActivityEYES
P0135Front Heated Oxygen Sensor Heater Circuit Not FunctioningEYES
P0137Rear Heated Oxygen Sensor Low VoltageEYES
P0138Rear Heated Oxygen Sensor High VoltageEYES
P0140Rear Heated Oxygen Sensor No ActivityEYES
P0141Rear Heated Oxygen Sensor Heater MalfuctionEYES
P0171Fuel Trim System Too LeanEYES
P0172Fuel Trim System Too RichEYES
P0222Main Throttle Idle Actuactor (MTIA) Low VoltageAYES
P0223Main Throttle Idle Actuactor (MTIA) High VoltageAYES
P0261Injector 1 Low VoltageAYES
P0262Injector 1 High VoltageAYES
P0264Injector 2 Low VoltageAYES
P0265Injector 2 High VoltageAYES
P0267Injector 3 Low VoltageAYES
P0268Injector 3 High VoltageAYES
P0270Injector 4 Low VoltageAYES
P0271Injector 4 High VoltageAYES
P0300Multiple Cylinder Misfire (Catalyst Damage)ABLINKING

1F – 112IENGINE CONTROLS
DAEWOO V–121 BL4
DTCIlluminate MIL Error
Type Function
P0300Multiple Cylinder Misfire (Increase Emission)EYES
P0327Knock Sensor Circuit Fault (1.4L DOHC)CnlNO
P0327Knock Sensor Circuit Fault (1.6L DOHC)EYES
P0335Magnetic Crankshaft Position Sensor Electrical ErrorEYES
P033658X Crankshaft Position Sensor Extra/missing PulseEYES
P033758X Crankshaft Sensor No SignalEYES
P0341Camshaft Position Sensor RationalityEYES
P0342Camshaft Position Sensor No SignalEYES
P0351Ignition Signal Coil A FaultAYES
P0352Ignition Signal Coil B FaultAYES
P0400Exhaust Gas Recirculation Out of LimitEYES
P0404Exhaust Gas Recirculation (EGR) PpendEYES
P0405EGR Pintle Position Sensor Low VoltageEYES
P0406EGR Pintle Position Sensor High voltageEYES
P0420Catalyst Low EfficiencyAYES
P0444EVAP Purge Control Circuit No SignalEYES
P0445EVAP Purge Control Circuit FaultEYES
P0462Fuel Level Sensor Low Voltage (1.6L DOHC Only)CnlNO
P0463Fuel Level Sensor High Voltage (1.6L DOHC Only)CnlNO
P0480Low Speed Cooling Fan Relay Circuit Fault (1.4L DOHC)EYES
P0480Low Speed Cooling Fan Relay Circuit Fault (1.6L DOHC)CnlNO
P0481High Speed Cooling Fan Relay High Voltage (1.4L DOHC)EYES
P0481High Speed Cooling Fan Relay High Voltage (1.6L DOHC)CnlNO
P0501Vehicle Speed No Signal (M/T Only)AYES
P0510Throttle Positon Switch Circuit Fault (1.4L DOHC)CnlNO
P0510Throttle Positon Switch Circuit Fault (1.6L DOHC)AYES
P0532A/C Pressure Sensor Low VoltageCnlNO
P0533A/C Pressure Sensor High VoltageCnlNO
P0562System Voltage (Engine Side) Too LowCnlNO
P0563System Voltage (Engine Side) Too HighCnlNO
P0601Engine Control Module Checksum ErrorEYES
P0604Engine Control Module RAM ErrorEYES
P0605Engine Control Module INMVY Write ErrorEYES
P0656Fuel Level Gauge High Circuit FaultCnlNO
P1181Variable Intake Manifold Solenoid Low VoltageEYES
P1182Variable Intake Manifold Solenoid High VoltageEYES
P1230Fuel Pump Relay Low Voltage (1.4L DOHC)CnlNO
P1230Fuel Pump Relay Low Voltage (1.6L DOHC)AYES
P1231Fuel Pump Relay High Voltage (1.4L DOHC)CnlNO
P1231Fuel Pump Relay High Voltage (1.6L DOHC)AYES
P1320Crankshaft Segment Period Segment Adaptation At LimitEYES

1F – 114IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0107
MANIFOLD ABSOLUTE PRESSURE SENSOR LOW
VOLTAGE
Circuit Description
The engine control module (ECM) uses the Manifold Ab-
solute Pressure (MAP) sensor to control the fuel delivery
and the ignition timing. The MAP sensor measures the
changes in the intake manifold pressure, which results
from engine load (intake manifold vacuum) and the rpm
changes; and converts these into voltage outputs. The
ECM sends a 5 volt–reference voltage to the MAP sensor.
As the manifold pressure changes, the output voltage of
the MAP sensor also changes. By monitoring the MAP
sensor output voltage, the ECM knows the manifold pres-
sure. A low–pressure (low voltage) output voltage will be
about 1.0 to 1.5 volts at idle, while higher pressure (high
voltage) output voltage will be about 4.5 to 4.8 at wide
open throttle (WOT). The MAP sensor is metric pressure,
allowing the ECM to make adjustments for different alti-
tudes.
Conditions for Setting the DTC
S This DTC can be stored in ”key–on” status.
(Case A)
S When the engine idling.
S No throttle position(TP) sensor MTIA fail conditions
present.
S Engine speed(rpm) is less than 2,500rpm.
S The MAP is less than 12.0 kPa.
(Case A)
S When the engine part load.
S The engine revolution speed is less than 4,000rpm.S No Throttle Position (TP) Sensor fails conditions
present.
S The Throttle Position (TP) angle greather than
30.0°.
S The MAP is less than 11.5 kPa.
S An open or low voltage condition exists.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illumi-
nate.
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 coolant fan turns ON.
S The ECM will substitutes a fixed MAP value and
use TP to control the fuel delivery (the scan tool will
not show defaulted)
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 DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
With the ignition ON and the engine stopped, the manifold
pressure is equal to atmosphere pressure and the signal
voltage will be high.

ENGINE CONTROLS 1F – 117
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0108
MANIFOLD ABSOLUTE PRESSURE SENSOR HIGH
VOLTAGE
Circuit Description
The engine control module (ECM) uses the Manifold Ab-
solute Pressure (MAP) sensor to control the fuel delivery
and the ignition timing. The MAP sensor measures the
changes in the intake manifold pressure, which results
from engine load (intake manifold vacuum) and the rpm
changes; and converts these into voltage outputs. The
ECM sends a 5 volt–reference voltage to the MAP sensor.
As the manifold pressure changes, the output voltage of
the MAP sensor also changes. By monitoring the MAP
sensor output voltage, the ECM knows the manifold pres-
sure. A low–pressure (low voltage) output voltage will be
about 1.0 to 1.5 volts at idle, while higher pressure (high
voltage) output voltage will be about 4.5 to 4.8 at wide
open throttle (WOT). The MAP sensor is metric pressure,
allowing the ECM to make adjustments for different alti-
tudes.
Conditions for Setting the DTC
S This DTC can be stored in ”key–on” status.
S When the engine idling.
S Engine speed is greater than 700rpm.
S No throttle position sensor (TPS) fail conditions
present.
S The MAP is greater than 95kPA.
S A high voltage condition exists.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illumi-
nate.
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 ECM will substitutes a fixed MAP value and
use TP to control the fuel delivery (the scan tool will
not show defaulted)
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 DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.
Diagnostic Aids
With the ignition ON and the engine stopped, the manifold
pressure is equal to atmosphere pressure and the signal
voltage will be high.
The ECM as an indication of vehicle altitude uses this in-
formation. Comparison of this reading with a known good
vehicle with the same sensor is a good way to check the
accuracy of a suspect sensor. Readings should be the
same ±0.4volt.
If a DTC P0108 is intermittent, refer to ”Manifold Absolute
Pressure Check” in this section for further diagnosis.
If the connections are OK monitor the manifold absolute
pressure(MAP) sensor signal voltage while moving re-
lated connectors and the wiring harness. If the failure is in-
duced, the display on the scan tool will change. This may
help to isolate the location of an intermittent malfunction.

1F – 158IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0171
FUEL TRIM SYSTEM TOO LEAN
System Description
If the adaptation value threshold is permanently exceed-
ed, the deviation of the adaptive terms enables to detect
a slow default coming out. Two time counters (one for the
rich side and another one for the lean side) are increased
while the lambda controller exceeds the adaptation
thresholds. As soon as one of the time counters reaches
its maximum value, the error is detected.
The aim of this test is to simulate a failure that would result
in exceeding the adaptive terms. Two kinds of failure must
be created.
S A lean side deviation: P0171
S A rich side deviation : P0172
It is thus necessary to determine, for each kind of failure,
the limit good and the limit bad. For a given failure, mea-
sure the emission threshold until the legal emission
thresholds are exceeded.
Note that the problem is due to the emission thresholds re-
quired, it is not simple to disturb the system so that the
emission thresholds will be exceeded. The tuning has
been made thanks to a dedicated calibration but, as such
a procedure is not permitted by the regulation, it is neces-
sary to create some material malfunction (fuel pressure
regulator, fuel injector, air leakage...).
Conditions for Setting the DTC
S DTCs P0107, P0108, P0112, P0113, P0117,
P0118, P0122, P0123, P0131, P0132, P0337,
P0338, P0341, P0342, P0400, P1319, P1402,
P1404, P1405, P1671 and P1672 are not set.
S Coolant temperature is greater than 20°C (68°F).
(1.4L DOHC)
S Coolant temperature is greater than 80°C (176°F).
(1.6L DOHC)
S Manifold Absolute Pressure (MAP) is greater than
70 kPa (10.2 psi).
S System is in closed loop.
Action Taken When the DTC Sets
S The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive trip with a fail.
S The ECM will record operating conditions at the
time the diagnostic fail. 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 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 DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for 10 sec-
onds.
Diagnostic Aids
Important : After repairs, use the scan tool Fuel Trim Re-
set function to reset the long–term fuel trim to 128 (0%).
S Fuel pressure – The system will be lean if the pres-
sure is too low. It may be necessary to monitor fuel
pressure while driving the vehicle at various road
speeds and/or loads to confirm.
S 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. Discon-
necting the MAP sensor will allow the ECM to sub-
stitute a fixed (default) value for the MAP sensor. If
the lean condition is gone when the sensor is dis-
connected, 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 P0171.
Check for poor O2S or MAP sensor connection at the
ECM. Inspect the harness 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 O2S display on the scan tool
while moving the connectors and the wiring harness re-
lated to the engine harness. A change in the display will
indicate the location of the fault.
Check the brake power booster check valve for possible
leaks.

ENGINE CONTROLS 1F – 159
DAEWOO V–121 BL4
DTC P0171 – Fuel Trim System Too Lean
StepActionValue(s)YesNo
1Perform an Euro On–Board Diagnostic (EOBD)
System Check.
Is the system check complete?–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
applicable 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 below the specified
value?27%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 go below the
specified value while operating under the specified
conditions?27%Go to Step 16Go to Step 5
5Visually/physically check the following items:
S Vacuum hoses for splits, kinks and improper
connections.
S Crankcase ventilation oil/air separator for prop-
er installation.
S Exhaust system for corrosion, leaks, loose or
missing hardware.
S Oxygen sensor (O2S) is installed securely and
the pigtail harness is not contacting exhaust
manifold or engine.
S Fuel for excessive water, alcohol, or other con-
taminants.
S Engine Control Module (ECM) and sensor
grounds are clean, tight, and in their proper
locations.
Do any of the above checks isolate a condition re-
quiring repair?–Go to Step 7Go to Step 6
61. Disconnect the Manifold Absolute Pressure
(MAP) sensor electrical connector.
2. Operate the vehicle in Closed Loop while moni-
toring the Long Term Fuel Trim value.
Is the Long Term Fuel Trim value below the specified
value?27%Go to Step 15Go to Step 9
71. Repair the malfunction found in Step 5.
2. Recheck the Long Term Fuel Trim value while
operating the engine.
Is the Long Term Fuel Trim value below the specified
value?27%Go to Step 8Go to Step 9

1F – 160IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
8Lean condition is not present.
Does a driveability problem exist?–Go to
”Symptom
Diagnosis”Go to Step 16
91. Visually/physically inspect the following items
for vacuum leaks:
S Intake manifold.
S Throttle body.
S Injector O–rings.
2. Repair any leaks found as necessary.
Is the repair complete?–Go to Step 16Go to Step 16
10Allow the engine to idle.
Are the Idle Air Control (IAC) counts above the spe-
cified value?5Go to Step 11Go to Step 12
11Check the fuel for excessive water, alcohol, or other
contaminants and correct the contaminated fuel
condition if present.
Is the repair complete?–Go to Step 16Go to Step 13
12Check the IAC valve performance. Refer to ”DTC
P0506 Idle Speed RPM Lower Than Desired Idle
Speed” or ”DTC P0507 Idle Speed RPM Higher
Than Desired Idle Speed” in this section and repair
as necessary.
Is the repair complete?–Go to Step 16Go to Step 13
131. Connect a fuel pressure gauge to the fuel sys-
tem.
2. Turn the ignition OFF for at least 10 seconds.
3. Turn the ignition ON, with the engine OFF. The
fuel pump will run for approximately 2–3 sec-
onds. It may be necessary to cycle the ignition
switch ON more than once to obtain maximum
fuel pressure.
4. Note the fuel pressure with the fuel pump run-
ning. The pressure should be within the speci-
fied value. When the fuel pump stops, the pres-
sure may vary slightly then hold steady.
Is the fuel pressure steady and does the fuel pres-
sure hold?241–276 kPa
(35–40 psi)Go to Step 14Go to
”Fuel System
Diagnosis”
141. Start and idle the engine at normal operating
temperature.
2. The fuel pressure noted in the above step
should drop by the indicated value.
Does the fuel pressure drop by the indicated value?21–69 kPa
(3–10 psi)Go to
”Fuel Injector
Balance Test”Go to
”Fuel System
Diagnosis”
15Replace the MAP sensor.
Is the action complete?–Go to Step 16–

1F – 162IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0172
FUEL TRIM SYSTEM TOO RICH
System Description
If the adaptation value threshold is permanently exceed-
ed, the deviation of the adaptive terms enables to detect
a slow default coming out. Two time counters (one for the
rich side and another one for the lean side) are increased
while the lambda controller exceeds the adaptation
thresholds. As soon as one of the time counters reaches
its maximum value, the error is detected.The aim of this
test is to simulate a failure that would result in exceeding
the adaptive terms. Two kinds of failure must be created.
S A lean side deviation: P0171
S A rich side deviation : P0172
It is thus necessary to determine, for each kind of failure,
the limit good and the limit bad. For a given failure, mea-
sure the emission threshold until the legal emission
thresholds are exceeded.Note that the problem is due to
the emission thresholds required, it is not simple to disturb
the system so that the emission thresholds will be exceed-
ed. The tuning has been made thanks to a dedicated cal-
ibration but, as such a procedure is not permitted by the
regulation, it is necessary to create some material mal-
function (fuel pressure regulator, fuel injector, air leak-
age...).
Conditions for Setting the DTC
S DTCs P0107, P0108, P0112, P0113, P0117,
P0118, P0122, P0123, P0131, P0132, P0337,
P0338, P0341, P0342, P0400, P1319, P1402,
P1404, P1405, P1671 and P1672 are not set.
S Coolant temperature is greater than 20°C (68°F).
(1.4L DOHC)
S Coolant temperature is greater than 80°C (176°F).
(1.6L DOHC)
S Manifold Absolute Pressure (MAP) is greater than
70 kPa (10.2 psi).
S System is in closed loop.
Action Taken When the DTC SetsS The Malfunction Indicator Lamp (MIL) will illuminate
after three consecutive trip with a fail.
S The ECM will record operating conditions at the
time the diagnostic fail. 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 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 DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for 10 sec-
onds.
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 O2S display on the scan tool
while moving the connectors and the wiring harness re-
lated 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.
DTC P0172 – Fuel Trim System Too Rich
StepActionValue(s)YesNo
1Perform an Euro On–Board Diagnostic (EOBD)
System Check.
Is the system check complete?–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
applicable DTC
tableGo to Step 3

ENGINE CONTROLS 1F – 163
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
3With the engine running, operate the vehicle until the
LOOP STATUS indicates closed.
Is the Long Term Fuel Trim value above the specified
value?–30%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?–30%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
111. Turn the ignition OFF.
2. Disconnect the Manifold Absolute Pressure
(MAP) sensor electrical connector.
3. Start the engine.
4. Operate the vehicle in Closed Loop while moni-
toring the Long Term Fuel Trim value.
Does the Long Term Fuel Trim value increase above
the specified value?–30%Go to Step 20Go to Step 12
12Check the IAC valve performance. Refer to ”DTC
P0506 Idle Speed RPM Lower Than Desired Idle
Speed” or ”DTC P0507 Idle Speed RPM Higher
Than Desired Idle Speed” in this section and repair
as necessary.
Is the repair complete?–Go to Step 21Go to Step 13