2004 DAEWOO LACETTI Ground

ENGINE CONTROLS 1F – 149
DAEWOO V–121 BL4
S Check for an intermittent ground in the wire be-
tween the O2 sensor and the engine control mod-
ule.
S Perform an injector 2alance test to determine if a
restricted fuel injector may be causing the lean con-
dition.S Vacuum of crankcase leaks will cause a lean run-
ning condition.
S An exhaust manifold gasket leak of a cracked ex-
haust manifold may cause outside air to be pulled
into the exhaust and past the sensor.
DTC P0137 – Rear Heated Oxygen Sensor Low Voltage
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. Turn the ignition switch to ON, with the engine
OFF.
2. Install a scan tool.
3. Engine at operating temperature.
4. Run the engine at 1,200rpm.
Does the scan tool the downstream oxygen (O2)
sensor1 voltage within the value specified?0.07–0.52VGo to Step 4Go to Step 3
3Does the scan tool the heated oxygen (O2) sensor1
voltage within the value specified?0.1VGo to Step 9Go to
”Diagnostic
Aids”
41. Turn the ignition switch to LOCK.
2. Disconnect the Heated O2 sensor connector
and engine control module (ECM) connector.
3. Check the Heated O2 sensor wire between the
Heated O2 sensor connector terminal 3 and
ECM connector terminal 36 for short to ground.
Is the problem found?–Go to Step 5Go to Step 6
51. Repair the wire of the connector terminal as
needed.
2. Clear the DTCs from the ECM.
3. Road tests the vehicle.
4. Perform the diagnostic system check.
Is the repair complete?–System OK–
61. Turn the ignition switch to LOCK.
2. Disconnect the Heated O2 sensor connector
and engine control module (ECM) connector.
3. Check the O2 sensor wire between the O2
sensor connector terminal 2 and ECM connec-
tor terminal 64 for short to ground.
Is the problem found?–Go to Step 7Go to Step 8
71. Repair the wire of the connector terminal as
needed.
2. Clear the DTCs from the ECM.
3. Road tests the vehicle.
4. Perform the diagnostic system check.
Is the repair complete?–System OK–
81. Turn the ignition switch to LOCK.
2. Replace the Heated O2 sensor.
3. Road tests the vehicle.
4. Perform the diagnostic system check.
Is the replacement complete?–Go to Step 10–

ENGINE CONTROLS 1F – 151
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0138
REAR HEATED OXYGEN SENSOR HIGH VOLTAGE
Circuit Description
The engine control module (ECM) supplies a voltage of
about 450mm volts between the ECM terminals 64 and 16.
The Heated oxygen (O2) sensor varies the voltage within
a range of about 1volt if the exhaust is rich, down to about
100mm volts if the exhaust is lean. The Heated O2 sensor
is like an open circuit and produces no voltage when it is
below 360°C(600°F). An open O2 sensor circuit or a cold
O2 sensor causes ”open loop” operation.
Conditions for Setting the DTC
S The Heated oxygen sensor voltage is more than
1.2V.
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/DTCS 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
S Normal scan tool voltage varies between 0.1volts
and 0.9volts while in closed loop.
S Inspect the oxygen (O2) sensor wire. The O2 sen-
sor may be positioned incorrectly and contacting
the exhaust manifold.
S Check for an intermittent ground in the wire be-
tween the O2 sensor and the engine control mod-
ule.
S Perform an injector balance test to determine if a
restricted fuel injector may be causing the lean con-
dition.
S Vacuum of crankcase leaks will cause a lean run-
ning condition.
S An exhaust manifold gasket leak of a cracked ex-
haust manifold may cause outside air to be pulled
into the exhaust and past the sensor.

1F – 154IENGINE CONTROLS
DAEWOO V–121 BL4
Diagnostic Aids
Normal scan tool voltage varies between 0.15 to 8.5mV
while in Closed Loop. If DTC P0140 is intermittent, refer
to ”Intermittents” in this section.
DTC P0140 – Rear Heated Oxygen Sensor No Activity
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. Run the engine to above the specified operat-
ing temperature.
2. Install a scan tool.
3. Operate the engine above the specified rpm for
2 minuets.
Does the scan tool the indicate Closed Loop?80°C(176°F)
1,200rpmGo to Step 3Go to Step 4
31. Turn the Turn the ignition switch to ON.
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 scan tool the indicate Closed Loop?–Go to Step 12Go to Step 4
4Disconnect the Heated O2 sensor connector and
jumper the Heated O2 sensor low circuit, terminal 3
to ground.
Is the HO2 voltage below the specified value and
does the scan tool indicate the heated oxygen sen-
sor heater voltage within the specified value?0.5VGo to Step 5Go to Step 6
5Check the Heated O2 sensor connector for malfunc-
tion terminals or poor connection and repair as nec-
essary.
Is repair necessary?–Go to Step 12Go to Step 9
61. Turn the ignition switch to On.
2. Remove the jumper wire.
3. Using a digital voltmeter(DVM), measure the
voltage between the Heated O2 sensor signal
circuit, terminal 4 to ground.
Does the Heated O2 sensor voltage measure above
the specified value?0.6VGo to Step 10Go to Step 9
7Does the Heated O2 sensor voltage measure below
the specified value?0.3VGo to Step 11Go to Step 8
8Check the Heated O2 sensor ground circuit, termi-
nal 3 for an open or poor connection and repair as
necessary.
Is repair necessary?–Go to Step 12Go to Step 8
9Check the Heated O2 sensor signal circuit, terminal
4 for an open or poor connection and repair as nec-
essary.
Is repair necessary?–Go to Step 12Go to Step 8

1F – 156IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0141
REAR HEATED OXYGEN SENSOR HEATER
MALFUNCTION
Circuit Description
The engine control module (ECM) supplies a voltage of
about 450mm volts between the ECM terminals 14 and 16.
The oxygen (O2) sensor varies the voltage within a range
of about 1volt if the exhaust is rich, down to about 100mm
volts if the exhaust is lean. The O2 sensor is like an open
circuit and produces no voltage when it is below
360°C(600°F). An open O2 sensor circuit or a cold O2
sensor causes ”open loop” operation.
Conditions for Setting the DTC
S The heated O2 sensor heater resistance is less
than 0 W or greater than 160 W. (1.4L DOHC)
S The heated O2 sensor heater resistance is less
than 10 W or greater than 30 W. (1.6L DOHC)
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.S The coolant fan turns ON.
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
S Normal scan tool voltage varies between 0.1volts
and 0.9 volts while in closed loop.
S Inspect the oxygen (O2) sensor wire. The O2 sen-
sor may be positioned incorrectly and contacting
the exhaust manifold.
S Check for an intermittent ground in the wire be-
tween the O2 sensor and the engine control mod-
ule.
S Perform an injector 2alance test to determine if a
restricted fuel injector may be causing the lean con-
dition.
S Vacuum of crankcase leaks will cause a lean run-
ning condition.

ENGINE CONTROLS 1F – 157
DAEWOO V–121 BL4
S An exhaust manifold gasket leak of a cracked ex-
haust manifold may cause outside air to be pulled
into the exhaust and past the sensor.
DTC P0141 – Rear Heated Oxygen Sensor Heater Malfunction
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. Turn the ignition switch to LOCK.
2. Disconnect the Heated O2 sensor connector
and engine control module (ECM) connector.
3. Check the Heated O2 sensor heater wire be-
tween the Heated O2 sensor connector termi-
nal 3 and ECM connector terminal 16 for an
open or short to ground.
Is the problem found?–Go to Step 3Go to Step 4
31. Repair the wire of the connector terminal as
needed.
2. Clear the DTCs from the ECM.
3. Road tests the vehicle.
4. Perform the diagnostic system check.
Is the repair complete?–System OK–
41. Turn the ignition switch to LOCK.
2. Replace the Heated O2 sensor.
3. Road tests the vehicle.
4. Perform the diagnostic system check.
Is the replacement complete?–Go to Step 6–
5Check if any additional DTCs are set.
Are any DTCs displaced that have not been diag-
nosed?–Go to applica-
ble DTC tableSystem OK

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 – 166IENGINE CONTROLS
DAEWOO V–121 BL4
DTC P0222 – Main Throttle Idle Actuator (MTIA) Low Voltage
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. Connect the scan tool to the DLC.
2. Turn the ignition switch to ON.
3. Press the accelerator pedal while watching
TPS for smooth changes in the voltage.
Does the scan tool show the TPS voltage change
smoothly within the value specified?0.3V–4.8VGo to
”Diagnostic
Aids”Go to Step 3
31. Turn the ignition switch to LOCK.
2. Disconnect the MTIA connector.
3. Measure the voltage between terminal 1 and 5.
Does the voltage measure within the value speci-
fied?4.8–5.0VGo to Step 4Go to Step 5
4Connect a fused jumper between the MTIA connec-
tor terminal 1 and terminal 6.
Does the scan tool show the TPS voltage above val-
ue specified?More than
4.8–5.0VGo to Step 10Go to Step 8
5Measure the voltage between the MTIA connector
1 and ground.
Does the voltage measure within the value speci-
fied?Below 5.0VGo to Step 6Go to Step 7
61. Turn the ignition switch to LOCK.
2. Disconnect the engine control module(ECM).
3. Check for a short to ground in the wire be-
tween the MTIA connector 5 and ECM connec-
tor 62.
Is the problem found?–Go to Step 9Go to Step 11
71. Turn the ignition switch to LOCK.
2. Check for a short to ground in the wire be-
tween the MTIA connector 1 and ECM connec-
tor 61.
Is the problem found?–Go to Step 9Go to Step 11
81. Turn the ignition switch to LOCK.
2. Check for a short to ground in the wire be-
tween the MTIA connector 6 and ECM connec-
tor 55.
Is the problem found?–Go to Step 9Go to Step 11
91. Repair the wire or the connector terminal as
needed.
2. Clear any DTCs from ECM.
3. Perform the Diagnostic System Check.
Is the repair complete?–System OK–
101. Replace the throttle body assembly.
2. Clear any DTCs from ECM.
3. Perform the Diagnostic System Check.
Is the repair complete?–System OK–

ENGINE CONTROLS 1F – 169
DAEWOO V–121 BL4
DTC P0223 – Main Throttle Idle Actuator (MTIA) High Voltage
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. Connect the scan tool to the DLC.
2. Turn the ignition switch to ON.
3. Press the accelerator pedal while watching
TPS for smooth changes in the voltage.
Does the scan tool show the TPS voltage change
smoothly within the value specified?0.3V–4.8VGo to
”Diagnostic
Aids”Go to Step 3
31. Turn the ignition switch to LOCK.
2. Disconnect the MTIA connector.
3. Measure the voltage between terminal 1 and 5.
Does the voltage measure within the value speci-
fied?4.8–5.0VGo to Step 4Go to Step 5
4Connect a fused jumper between the MTIA connec-
tor terminal 1 and terminal 6.
Does the scan tool show the TPS voltage above val-
ue specified?More than
4.8–5.0VGo to Step 10Go to Step 8
5Measure the voltage between the MTIA connector
1 and ground.
Does the voltage measure within the value speci-
fied?Below 5.0VGo to Step 6Go to Step 7
61. Turn the ignition switch to LOCK.
2. Disconnect the engine control module(ECM).
3. Check for an open or short to battery voltage in
the wire between the MTIA connector 5 and
ECM connector 62.
Is the problem found?–Go to Step 9Go to Step 11
71. Turn the ignition switch to LOCK.
2. Check for an open or short to battery voltage in
the wire between the MTIA connector 1 and
ECM connector 61.
Is the problem found?–Go to Step 9Go to Step 11
81. Turn the ignition switch to LOCK.
2. Check for an open or short to battery voltage in
the wire between the MTIA connector 6 and
ECM connector 55.
Is the problem found?–Go to Step 9Go to Step 11
91. Repair the wire or the connector terminal as
needed.
2. Clear any DTCs from ECM.
3. Perform the Diagnostic System Check.
Is the repair complete?–System OK–
101. Replace the throttle body assembly.
2. Clear any DTCs from ECM.
3. Perform the Diagnostic System Check.
Is the repair complete?–System OK–