2004 DAEWOO LACETTI Iat

1F – 106IENGINE CONTROLS
DAEWOO V–121 BL4
DATA LINK CONNECTOR DIAGNOSIS (1.4L/1.6L DOHC)
Circuit Description
The provision for communicating with the Engine Control
Module (ECM) is the Data Link Connector (DLC). It is lo-
cated under the instrument panel. The DLC is used to con-
nect the scan tool. Battery power and ground is supplied
for the scan tool through the DLC. The Keyword 2000 seri-
al data circuit to the DLC allows the ECM to communicate
with the scan tool. A Universal Asynchronous Receiver
Transmitter (UART) serial data line is used to communi-
cate with the other modules such as the Electronic Brake
Control Module (EBCM), the Supplemental Inflatable Re-
straint (SIR) system. and the Instrument Panel Cluster.
Diagnostic Aids
Ensure that the correct application (model line, car year,
etc.) has been selected on the scan tool. If communication
still cannot be established, try the scan tool on another ve-
hicle to ensure that the scan tool or cables are not the
cause of the condition.
An intermittent may be caused by a poor connection,
rubbed through wire insulation, or a broken wire inside the
insulation.
Any circuitry that is suspected of causing an intermittent
complaint should be thoroughly checked for the following
conditions:
S Backed–out terminals.S Improper mating of terminals.
S Broken locks.
S Improperly formed or damaged terminals.
S Poor terminal–to–wiring connection.
S Physical damage to the wiring harness.
S Corrosion.
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. Unlike the UART serial data circuit, the only time a
Class II serial data circuit has any voltage on it is
when a scan tool asks the ECM for information and
sends the information out.
5. Locate and repair any shorts that may have caused
the fuse to open before replacement, if the no volt-
age condition was due to an open fuse.
10. The scan tool or associated cables could be mal-
functioning. Refer to the scan tool’s manual for re-
pair information.

1F – 108IENGINE CONTROLS
DAEWOO V–121 BL4
DATA LINK CONNECTOR DIAGNOSIS (1.8L DOHC)
Circuit Description
The provision for communicating with the Engine Control
Module (ECM) is the Data Link Connector (DLC). It is lo-
cated under the instrument panel. The DLC is used to con-
nect the scan tool. Battery power and ground is supplied
for the scan tool through the DLC. The Keyword 2000 seri-
al data circuit to the DLC allows the ECM to communicate
with the scan tool. A Universal Asynchronous Receiver
Transmitter (UART) serial data line is used to communi-
cate with the other modules such as the Electronic Brake
Control Module (EBCM), the Supplemental Inflatable Re-
straint (SIR) system. and the Instrument Panel Cluster.
Diagnostic Aids
Ensure that the correct application (model line, car year,
etc.) has been selected on the scan tool. If communication
still cannot be established, try the scan tool on another ve-
hicle to ensure that the scan tool or cables are not the
cause of the condition.
An intermittent may be caused by a poor connection,
rubbed through wire insulation, or a broken wire inside the
insulation.
Any circuitry that is suspected of causing an intermittent
complaint should be thoroughly checked for the following
conditions:
S Backed–out terminals.S Improper mating of terminals.
S Broken locks.
S Improperly formed or damaged terminals.
S Poor terminal–to–wiring connection.
S Physical damage to the wiring harness.
S Corrosion.
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. Unlike the UART serial data circuit, the only time a
Class II serial data circuit has any voltage on it is
when a scan tool asks the ECM for information and
sends the information out.
5. Locate and repair any shorts that may have caused
the fuse to open before replacement, if the no volt-
age condition was due to an open fuse.
10. The scan tool or associated cables could be mal-
functioning. Refer to the scan tool’s manual for re-
pair information.

1F – 120IENGINE CONTROLS
DAEWOO V–121 BL4
J3B11F51
BRNORN
/BLK
DIAGNOSTIC TROUBLE CODE (DTC) P0112
INTAKE AIR TEMPERATURE SENSOR LOW VOLTAGE
Circuit Description
The Intake Air Temperature (IAT) Sensor uses a thermis-
tor to control the signal voltage to the engine control mod-
ule (ECM). The ECM supplies a 5 volt reference voltage
and a ground to the sensor. When the air is cold, the resist-
ance is high ; therefore IAT sensor signal voltage will be
high. If the intake air is warm, resistance is low ; therefore
the IAT sensor signal voltage will be low.
Conditions for Setting the DTC
S IAT voltage is less than 0.01V.
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 ECM will default to 605C(1405F) for intake air
temperature. The scan tool will not show the de-
faulted value.
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
If the vehicle is at ambient temperature, compare the IAT
sensor to the engine coolant temperature(ECT) sensor.
The IAT sensor and the ECT sensor should be relatively
close to each other. Use the temperature vs. Resistance
Values table to evaluate the possibility of a skewed sensor.
Refer to ”Temperature vs. Resistance” in this section.

ENGINE CONTROLS 1F – 121
DAEWOO V–121 BL4
DTC P0112 – Intake Air Temperature 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. Connect the scan tool to the data link connec-
tor(DLC).
2. Run the engine until it reaches operating tem-
perature.
Does the scan tool show the IAT sensor reading
within the value specified?15~80°CGo to
”Diagnostic
Aids”Go to Step 3
31. Turn the ignition switch to LOCK.
2. Disconnect the IAT sensor connector.
3. Turn the ignition switch to ON.
Does the scan tool show the IAT sensor reading
within the value specified? –30°CGo to Step 4Go to Step 5
4Check for a faulty connector or terminals at the IAT
sensor connector.
Is the problem found?–Go to Step 7Go to Step 6
5Check for wire for a short to ground between the IAT
connector terminal 1 and the ECM connector termi-
nal 78.
Is the problem found?–Go to Step 7Go to Step 6
6Check for wire for a short to ECM reference voltage
between the IAT sensor connector terminal 2 and
the ECM connector terminal 13.
Is the problem found?4.5 – 5.5VGo to Step 7Go to Step 9
71. Turn the ignition switch to LOCK.
2. Repair the wire or the connector terminal as
needed.
3. Clear any DTCs from the ECM.
4. Run the engine until it reaches operating tem-
perature.
5. Perform the diagnostic system check.
Is the repair complete?–System OK–
81. Turn the ignition switch to LOCK.
2. Replace the IAT sensor.
3. Clear any DTCs from the ECM.
4. Run the engine until it reaches operating tem-
perature.
5. Perform the diagnostic system check.
Is the repair complete?–System OK–
91. Turn the ignition switch to LOCK.
2. Replace the engine control module(ECM).
3. Run the engine until it reaches operating tem-
perature.
4. Perform the diagnostic system check.
Is the repair complete?–Go to Step 10–
10Check if any additional DTCs are set.
Are any DTCs displaced that have not been diag-
nosed?–Go to the appli-
cable DTC
tableSystem OK

1F – 122IENGINE CONTROLS
DAEWOO V–121 BL4
J3B11F51
BRNORN
/BLK
DIAGNOSTIC TROUBLE CODE (DTC) P0113
INTAKE AIR TEMPERATURE SENSOR HIGH VOLTAGE
Circuit Description
The Intake Air Temperature (IAT) Sensor uses a thermis-
tor to control the signal voltage to the engine control mod-
ule (ECM). The ECM supplies a 5 volt reference voltage
and a ground to the sensor . when the air is cold, the resist-
ance is high ; therefore IAT sensor signal voltage will be
high. If the intake air is warm, resistance is low ; therefore
the IAT sensor signal voltage will be low.
Conditions for Setting the DTC
S IAT voltage is less than 4.99V.
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 ECM will default to 605C(1405F) for intake air
temperature. The scan tool will not show the de-
faulted value.
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 If the vehicle is at ambient temperature, compare
the IAT sensor to the engine coolant temperature
(ECT) sensor. The IAT sensor and the ECT sensor
should be relatively close to each other.
S Use the temperature vs. Resistance Values table to
evaluate the possibility of a skewed sensor. Refer
to ”Temperature vs. Resistance” in this section.

ENGINE CONTROLS 1F – 123
DAEWOO V–121 BL4
DTC P0113 – Intake Air Temperature Sensor 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 data link connec-
tor (DLC).
2. Run the engine unit it reaches operating tem-
perature.
Does the scan tool show the intake air temperature
(IAT) sensor reading within the value specified?15~80°C
(10~176°F)Go to
”Diagnostic
Aids”Go to Step 3
31. Turn the ignition switch to LOCK.
2. Disconnect the IAT sensor connector.
3. Jumper to IAT sensor connector terminals.
4. Turn the ignition switch to ON.
Does the scan tool show the IAT sensor reading the
value specified?180°C
(356°F)Go to Step 4Go to Step 5
4Check for a faulty connector or terminals 1 and 2 of
the IAT sensor connector.
Is the problem found?–Go to Step 10Go to Step 9
5Measure the voltage between terminals 1 and 2 of
IAT sensor connector.
Does the voltage measure within the value speci-
fied?4.5~5.5VGo to Step 11Go to Step 6
6Measure the voltage between the IAT sensor con-
nector terminal 2 and the battery ground(negative)
post.
Does the voltage measure within the value speci-
fied?4.5~5.5VGo to Step 7Go to Step 8
71. Turn the ignition switch to LOCK.
2. Check for an open or short to battery voltage in
the wire between the IAT sensor connector ter-
minal 2 and the engine control module(ECM)
connector terminal 13.
Is the problem found?–Go to Step 10Go 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 IAT sensor connector ter-
minal 1 and the ECM connector terminal 78.
Is the problem found?–Go to Step 10Go to Step 11
91. Turn the ignition switch to LOCK.
2. Replace the IAT sensor.
3. Clear any DTCs from the ECM.
4. Perform the diagnostic system check.
Is the repair complete?–System OK–
101. Turn the ignition switch to LOCK.
2. Repair the wire of the connector terminals as
needed.
3. Clear any DTCs from the ECM.
4. Perform the diagnostic system check.
Is the repair complete?–System OK–

1F – 126IENGINE CONTROLS
DAEWOO V–121 BL4
DTC P0117 – Engine Coolant Temperature 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. Connect the scan tool to the data link connec-
tor (DLC).
2. Run the engine until it reaches operating tem-
perature.
Does the scan tool show the ECT sensor reading
within the value specified?80~110°C
(176~260°F)Go to
”Diagnostic
Aids”Go to Step 3
31. Turn the ignition switch to LOCK.
2. Disconnect the ECT sensor connector.
3. Turn the ignition switch to ON.
Does the scan tool show the IAT sensor reading
within the value specified?–30°C
(–22°F)Go to Step 4Go to Step 6
41. Jumper the ECT sensor signal circuits at termi-
nal 1 and 2.
2. Turn the ignition switch to ON.
Does the scan tool show the ECT sensor reading
within the value specified?120°CGo to Step 5Go to Step 6
51. Replace the ECT sensor.
2. Clear any DTCs from the ECM.
3. Perform the diagnostic system check.
Is the replacement complete?–System OK–
6Measure the voltage between ECT terminal 2 and
ground.
Does the voltage measure within the value speci-
fied?4.5–5.5VGo to Step 7Go to Step 8
71. Turn the ignition switch to LOCK.
2. Disconnect the ECM wiring connector.
3. Check for a faulty connector or terminals at the
ECT sensor connectors and ECM connectors
for short to ECM reference voltage.
Is the problem found?–Go to Step 9Go to Step 8
81. Turn the ignition switch to LOCK.
2. Repair the wire of the connector terminals as
needed.
3. Clear any DTCs from the ECM.
4. Run the engine until it reaches operating tem-
perature.
5. Perform the diagnostic system check.
Is the repair complete?–System OK–

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.