2004 DAEWOO LACETTI engine controls

ENGINE CONTROLS 1F – 391
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0138
REAR HEATED OXYGEN SENSOR (HO2S2) HIGH
VOLTAGE
Circuit Description
In order to control emissions, a catalytic converter is used
to convert harmful emissions into harmless water vapor
and carbon dioxide.
The Engine Control Module (ECM) has the ability to moni-
tor this process by using a Rear Heated Oxygen Sensor
(HO2S2). The HO2S2, located in the exhaust stream past
the catalytic converter, produces an output signal which in-
dicates the storage capacity of the catalyst. This in turn in-
dicates the catalyst¡¯s ability to convert exhaust emissions
effectively. If the catalyst is functioning properly, the
HO2S2 signal will be far less active than the signal pro-
duced by the Front Heated Oxygen Sensor (HO2S1).
If the HO2S2 pigtail wiring, connector, or terminal is dam-
aged, the entire HO2S2 assembly must be replaced. Do
not attempt to repair the wiring, connector, or terminals. In
order for the sensor to function properly, it must have a
clean air reference provided to it. This clean air reference
is obtained by way of the HO2S2 wire(s). Any attempt to
repair the wires, connector, or terminals could result in the
obstruction of the air reference and degrade the HO2S2
performance.Conditions for Setting the DTC
S HO2S2 voltage is greater than 0.952 volt in Closed
Loop control or greater than 0.55 volt in Decel Fuel
Cutoff (DFCO) mode.
S Engine Coolant Temperature (ECT) is greater than
60°C (140°F).
S System voltage is greater than 10 volts.
S Closed Loop test: 3 seconds delay after in Closed
Loop and airflow is greater than 9 g/sec.
S DFCO test: 2 seconds delay after in DFCO.
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0171, P0172, P0201, P0202,
P0203, P0204, P0300, P0336, P0337, P0351,
P0352, P0141, P0402, P0404, P0405, P0406,
P0506, P0507, P1404, and P0443 are not set.
Action Taken When the DTC Sets
S 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 DTC is stored.

1F – 392IENGINE CONTROLS
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
Check for the following conditions:
S Rich exhaust – An overly rich exhaust may load the
catalyst, causing high HO2S2 signal voltages.
S Silicone contamination – A false rich condition may
be caused by silicone contamination of the HO2S2.
This will be indicated by a powdery white deposit on
the sensor.
S Faulty HO2S2 – If HO2S2 is internally shorted, the
HO2S2 voltage displayed on a scan tool will be
over 1 volt. Disconnect the HO2S2 and jumper the
sensor low circuit to engine ground; if the displayed
voltage goes from over 1000 millivolt to around 450
millivolt, replace the HO2S2.S Intermittent test – Observe HO2S2 on the scan tool
while moving related connectors and the wiring har-
ness with the key in the ON position. If the failure is
induced, the HO2S2 display will change. This may
help isolate the location of the malfunction.
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 P0138 is the result of
a hard failure or an intermittent condition.
5. Disconnecting the HO2S2 and jumpering the sen-
sor signal circuit and the sensor low circuit to
ground should cause the scan tool to display
HO2S2 voltage below 100 mv (0.1 v). If the signal
voltage is still high, the ECM is malfunctioning.
6. The replacement ECM must be reprogrammed.
Refer to the latest Techline procedure for ECM re-
programming.
DTC P0138 – Rear Heated Oxygen Sensor (HO2S2) High Voltage
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.
Is the Rear Heated Oxygen Sensor (HO2S2) volt-
age above the value specified?0.9 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.
Is the HO2S2 voltage above the specified value?0.9 VGo to Step 4Go to Step 9
41. Turn the ignition OFF.
2. Disconnect HO2S2 connector.
3. Disconnect the Engine Control Module (ECM)
connector.
4. With voltmeter connected to ground, probe the
HO2S2 high signal circuit, terminal K36.
Is the voltage within the specified value?±0 VGo to Step 5Go to Step 6

ENGINE CONTROLS 1F – 393
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
51. Reconnect the ECM connector.
2. Turn the ignition ON.
3. Jumper the high and low circuits at the HO2S2
connector, terminals 1 and 2 to ground.
Does the scan tool indicate the HO2S2 voltage be-
low the specified value?0.1 VGo to Step 7Go to Step 8
6Repair the short to voltage in the HO2S2 high circuit.
Is the repair complete?–Go to Step 9–
7S Turn the ignition OFF.
S Replace the HO2S2.
Is the repair complete?–Go to Step 9–
8S Turn the ignition OFF.
S Replace the ECM.
Is the repair complete?–Go to Step 9–
91. 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 10Go to Step 2
10Check if any additional DTCs are set.
Are any DTCs displayed that have not been diag-
nosed?–Go to
Applicable DTC
tableSystem OK

1F – 394IENGINE CONTROLS
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0140
REAR HEATED OXYGEN SENSOR (HO2S2) NO ACTIVITY
OR OPEN
Circuit Description
In order to control emissions, a catalytic converter is used
to convert harmful emissions into harmless water vapor
and carbon dioxide.
The Engine Control Module (ECM) has the ability to moni-
tor this process by using a Rear Heated Oxygen Sensor
(HO2S2). The HO2S2, located in the exhaust stream past
the catalytic converter, produces an output signal which in-
dicates the storage capacity of the catalyst. This in turn in-
dicates the catalyst is ability to convert exhaust emissions
effectively. If the catalyst is functioning properly, the
HO2S2 signal will be far less active than the signal pro-
duced by the Front Heated Oxygen Sensor (HO2S1).
If the HO2S2 pigtail wiring, connector, or terminal is dam-
aged, the entire HO2S2 assembly must be replaced. Do
not attempt to repair the wiring, connector, or terminals. In
order for the sensor to function properly, it must have a
clean air reference provided to it. This clean air reference
is obtained by way of the HO2S2 wire(s). Any attempt to
repair the wires, connector, or terminals could result in the
obstruction of the air reference and degrade the HO2S2
performance.Conditions for Setting the DTC
S HO2S2 voltage is between 0.422 and 0.478 volts.
S Engine Coolant Temperature (ECT) is greater than
60°C (140°F).
S Engine rum time is greater than 60 seconds.
S System voltage is greater than 10 volts.
S Closed Loop stoichiometry.
S 3 second delay after exiting Decel Fuel Cutoff
(DFCO) mode.
S DTCs P0106, P0107, P0108, P0117, P0118,
P0122, P0123, P0171, P0172, P0201, P0202,
P0203, P0204, P0300, P0336, P0337, P0351,
P0352, P0141, P0402, P0404, P0405, P0406,
P0506, P0507, P1404, and P0443 are not set.
Action Taken When the DTC Sets
S 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 DTC is stored.
Conditions for Clearing the MIL/DTC

ENGINE CONTROLS 1F – 395
DAEWOO V–121 BL4
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
An intermittent may be caused by a rubbed–through wire
insulation or a wire contacting the exhaust.
Check for the following conditions:
S A poor connection or a damaged harness – Inspect
the harness for a short to ground in the sensor sig-
nal circuit. Ensure that the HO2S2 pigtail is not con-
tacting the exhaust. Check for the following condi-
tions:
S Improper mating
S Broken locks
S Improperly formed
S Damaged terminals
S Poor terminal–to–wire connection
S Damaged harness
S Intermittent test – Observe HO2S2 on the scan tool
while moving the related connections and the wiringharness with the ignition ON. If the failure is in-
duced, the HO2S2 display will change. This may
help isolate the location of the malfunction.
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 P0140 is the result of
a hard failure or an intermittent condition.
4. Disconnecting the HO2S2 and jumpering the sen-
sor signal circuit and the sensor low circuit to
ground will determine if the ECM or wiring or
HO2S2 is malfunctioning.
6. Determines which circuit the malfunction is in. If the
sensor signal circuit and the sensor low circuit are
OK, then the ECM connection or ECM is malfunc-
tioning.
10. The replacement ECM must be reprogrammed.
Refer to the latest Techline procedure for ECM re-
programming.
DTC P0140 – Rear Heated Oxygen Sensor (HO2S2) No Activity or
Open
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 operate to normal operat-
ing temperature.
3. Run the engine above the specified rpm for two
minutes.
Does the scan tool display a Rear Heated Oxygen
Sensor (HO2S2) voltage between the value speci-
fied?80°C(176°F)
1200 rpm
422–478 mVGo to Step 4Go to Step 3
31. Allow the engine to idle.
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 display the HO2S2 voltage
steady around the value specified?422–478 mVGo to Step 11Go to Step 4

1F – 396IENGINE CONTROLS
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
41. Turn the ignition OFF.
2. Disconnect HO2S2 connector.
3. Turn the ignition ON.
4. Jumper the high and low circuits at the HO2S2
connector, terminals 1 and 2 to ground.
Does the scan tool indicate the HO2S2 voltage be-
low the specified value?0.1 VGo to Step 5Go to Step 6
51. Turn the ignition OFF.
2. Check for a malfunctioning connection at the
HO2S2 Engine Control Module (ECM) side and
repair as needed.
Is the repair complete?–Go to Step 11Go to Step 7
61. Remove the jumper wire.
2. With a voltmeter connected to ground, probe
the terminal 2 of the HO2S2.
Does the voltage within the specified value?4.5 VGo to Step 8Go to Step 9
71. Turn the ignition OFF.
2. Replace the HO2S2.
Is the repair complete?–Go to Step 11–
8Check the HO2S2 low circuit for an open or poor
connection and repair as needed.
Is the repair complete?–Go to Step 11Go to Step 10
91. Turn the ignition OFF.
2. Disconnect the ECM connector.
3. Check the HO2S2 high circuit for continuity
and repair as needed.
Is the repair complete?–Go to Step 11Go to Step 5
101. Turn the ignition OFF.
2. Replace the HO2S2.
Is the repair complete?–Go to Step 11–
111. 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 12Go to Step 2
12Check 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 – 397
DAEWOO V–121 BL4
DIAGNOSTIC TROUBLE CODE (DTC) P0141
REAR HEATED OXYGEN SENSOR (HO2S2) HEATER
CIRCUIT NOT FUNCTIONING
Circuit Description
In order to control emissions, a catalytic converter is used
to convert harmful emissions into harmless water vapor
and carbon dioxide.
The Engine Control Module (ECM) has the ability to moni-
tor this process by using a Rear Heated Oxygen Sensor
(HO2S2). The HO2S2, located in the exhaust stream past
the catalytic converter, produces an output signal which in-
dicates the storage capacity of the catalyst. This in turn in-
dicates the catalyst is ability to convert exhaust emissions
effectively. If the catalyst is functioning properly, the
HO2S2 signal will be far less active than the signal pro-
duced by the Front Heated Oxygen Sensor (HO2S1).
If the HO2S2 pigtail wiring, connector, or terminal is dam-
aged, the entire HO2S2 assembly must be replaced. Do
not attempt to repair the wiring, connector, or terminals. In
order for the sensor to function properly, it must have a
clean air reference provided to it. This clean air reference
is obtained by way of the HO2S2 wire(s). Any attempt to
repair the wires, connector, or terminals could result in the
obstruction of the air reference and degrade the HO2S2
performance.The ECM will check if HO2S2 is functioning properly by
monitoring the current to HO2S2 heater. If the current is
less than 0.1 ampere, DTC P0141 will set.
Conditions for Setting the DTC
S HO2S2 heater current is less than 0.1 amperes.
S Engine rum time is greater than 60 seconds.
S System voltage is greater than 10 volts.
Action Taken When the DTC Sets
S 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 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 The DTC(s) can be cleared by using the scan tool.
S Disconnecting the ECM battery feed for more than
10 seconds.

1F – 398IENGINE CONTROLS
DAEWOO V–121 BL4
Diagnostic Aids
An intermittent may be caused by a rubbed–through wire
insulation or a wire contacting the exhaust.
Check for a poor connection or a damaged harness – in-
spect the harness connectors for the following conditions:
S Improper mating
S Broken locks
S Improperly formed
S Damaged terminals
S Poor terminal–to–wire connection
S Damaged 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. This step determines if DTC P0141 is the result of
a hard failure or an intermittent condition. With the
ignition ON, engine OFF, the HO2S2 voltage dis-
played on the scan tool should change within sever-
al minutes toward 0 or 1 volt, indicating that the
heater is working properly.
3. Probing terminal D of the HO2S2 connector verifies
if voltage is available to the HO2S2 heater.
4. If voltage is available at the connector, than it be-
comes a good voltage source to check for a ground
at terminal 3.
5. Determines if voltage is not available at the HO2S2
due to an open in the HO2S2 fuse or open ignition
feed circuit. If the fuse is open, determine if it was
due to a short in the ignition feed circuit before re-
placing the fuse.
DTC P0141 – Rear Heated Oxygen Sensor (HO2S2) Heater Circuit
Not Functioning
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. Turn the ignition OFF.
2. Disconnect the Rear Heated Oxygen Sensor
(HO2S2) connector.
3. Turn the ignition ON.
4. Using a voltmeter, measure the voltage at ter-
minal 4 of HO2S2 and ground.
Is the voltage within the specified value?11–14 VGo to Step 3Go to
”Main Relay
Circuit Check”
31. Turn the ignition OFF.
2. Disconnect the HO2S2 connector.
3. Check the connections at HO2S2 connector,
terminal 3 and 4 and repair as needed.
Is the repair complete?–Go to Step 10Go to Step 4
4Disconnect the Engine control Module (ECM) con-
nector.
Check the connection at the ECM connector, termi-
nal M2 and repair as needed.–Go to Step 10Go to Step 5
51. Using ohmmeter, measure the resistance be-
tween terminal 3 of the HO2S2 and terminal
M2 of the ECM.
Is the resistance equal to the specified value?
1. Using a voltmeter, measure the voltage be-
tween terminal M2 of the ECM and ground.
Is the voltage within the specified value?0 Ω

0 VGo to Step 7Go to Step 6
6Repair an open or short to voltage circuit.
Is the repair complete?–Go to Step 10–