Page 321 of 2643

ENGINE CONTROLS 1F – 75
DAEWOO V–121 BL4
MANIFOLD ABSOLUTE PRESSURE CHECK
(1.4L/1.6L DOHC)
Circuit Description
The Manifold Absolute Pressure (MAP) sensor measures
the changes in the intake manifold pressure which result
from engine load (intake manifold vacuum) and rpm
changes. The MAP sensor converts these changes into a
voltage output. The engine control module (ECM) sends
a 5–volt reference voltage to the MAP sensor. As the in-
take manifold pressure changes, the output voltage of the
MAP sensor also changes. A low voltage (high vacuum)
output of 1 to 2 volts is present at idle. A high voltage (low
vacuum) output of 4.0 to 4.8 volts is present at wide open
throttle. The MAP sensor is also used under certain condi-
tions to measure baro–metric pressure. This allows the
ECM to make adjustments for altitude changes. The ECMuses the MAP sensor for fuel delivery and ignition timing
changes.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. Applying 34 kPa (10 inches Hg) of vacuum to the
MAP sensor should cause the voltage to change.
Subtract the second voltage reading from the first.
That voltage value should be more than 1.5 volts.
When applying vacuum to the MAP sensor, the
change in the voltage should happen instantly. A
slow voltage change indicates a faulty MAP sensor.
3. Disconnect the MAP sensor from the bracket and
twist the MAP sensor. Output changes more than
0.1 volt indicate a faulty connector or connection.
Page 322 of 2643

1F – 76IENGINE CONTROLS
DAEWOO V–121 BL4
Manifold Absolute Pressure Check (1.4L/1.6L DOHC)
StepActionValue(s)YesNo
11. Turn the ignition OFF.
2. Connect a scan tool to the Data Link Connec-
tor (DLC).
3. Turn the ignition ON.
4. Compare the Manifold Absolute Pressure
(MAP) sensor voltage reading from the scan-
ner with that from a known good vehicle.
Is the difference in the two voltage readings less
than the value specified?0.4 vGo to Step 2Go to Step 5
21. Turn the ignition OFF.
2. Connect a scan tool to the DLC.
3. Disconnect the MAP sensor vacuum line.
4. Connect a hand vacuum pump to the MAP
sensor.
5. Turn the ignition ON.
6. Note the MAP sensor voltage.
7. Apply 10 in. Hg (34 kPa) of vacuum to the
MAP sensor and note the voltage change.
Is the difference in voltage readings more than the
value specified?1.5 vSystem OKGo to Step 3
3Inspect the MAP sensor connector terminals.
Is the problem found?–Go to Step 4Go to Step 5
4Repair the MAP sensor connector terminals as
needed.
Is the repair complete?–System OK–
5Replace the MAP sensor.
Is the repair complete?–System OK–
Page 323 of 2643

ENGINE CONTROLS 1F – 77
DAEWOO V–121 BL4
MANIFOLD ABSOLUTE PRESSURE CHECK (1.8L DOHC)
Circuit Description
The Manifold Absolute Pressure (MAP) sensor measures
the changes in the intake manifold pressure which result
from engine load (intake manifold vacuum) and rpm
changes. The MAP sensor converts these changes into a
voltage output. The engine control module (ECM) sends
a 5–volt reference voltage to the MAP sensor. As the in-
take manifold pressure changes, the output voltage of the
MAP sensor also changes. A low voltage (high vacuum)
output of 1 to 2 volts is present at idle. A high voltage (low
vacuum) output of 4.0 to 4.8 volts is present at wide open
throttle. The MAP sensor is also used under certain condi-
tions to measure baro–metric pressure. This allows the
ECM to make adjustments for altitude changes. The ECMuses the MAP sensor for fuel delivery and ignition timing
changes.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. Applying 34 kPa (10 inches Hg) of vacuum to the
MAP sensor should cause the voltage to change.
Subtract the second voltage reading from the first.
That voltage value should be more than 1.5 volts.
When applying vacuum to the MAP sensor, the
change in the voltage should happen instantly. A
slow voltage change indicates a faulty MAP sensor.
3. Disconnect the MAP sensor from the bracket and
twist the MAP sensor. Output changes more than
0.1 volt indicate a faulty connector or connection.
Page 324 of 2643

1F – 78IENGINE CONTROLS
DAEWOO V–121 BL4
Manifold Absolute Pressure Check (1.8L DOHC)
StepActionValue(s)YesNo
11. Turn the ignition OFF.
2. Connect a scan tool to the Data Link Connec-
tor (DLC).
3. Turn the ignition ON.
4. Compare the Manifold Absolute Pressure
(MAP) sensor voltage reading from the scan-
ner with that from a known good vehicle.
Is the difference in the two voltage readings less
than the value specified?0.4 vGo to Step 2Go to Step 5
21. Turn the ignition OFF.
2. Connect a scan tool to the DLC.
3. Disconnect the MAP sensor vacuum line.
4. Connect a hand vacuum pump to the MAP
sensor.
5. Turn the ignition ON.
6. Note the MAP sensor voltage.
7. Apply 10 in. Hg (34 kPa) of vacuum to the
MAP sensor and note the voltage change.
Is the difference in voltage readings more than the
value specified?1.5 vSystem OKGo to Step 3
3Inspect the MAP sensor connector terminals.
Is the problem found?–Go to Step 4Go to Step 5
4Repair the MAP sensor connector terminals as
needed.
Is the repair complete?–System OK–
5Replace the MAP sensor.
Is the repair complete?–System OK–
Page 325 of 2643

ENGINE CONTROLS 1F – 79
DAEWOO V–121 BL4
IDLE AIR CONTROL SYSTEM CHECK (1.4L/1.6L DOHC)
Circuit Description
The aim of the MTIA (Main Throttle Idle Actuator) is to con-
trol the idle speed with the throttle body itself. The throttle
is motorized for low opening angle (0°C, 19°C). The char-
acteristics of the airflow are not the same for low and high
opening angles. As a matter of fact, the gradient of the
mass air flow function of TPS is lower for small angles that
permits to be more precise during the idle speed control.
Out of idle speed the throttle is actuated mechanically by
a classical bowdencable.
The main throttle idle actuator (MTIA) provides a voltagesignal that changes in relation to the throttle plate angle.
The signal voltage will vary from about nearly 5.0 V at idles
to about 0.2V to 0.4 V at wide–open throttle. The TPS is
one of the most important inputs used by the ECM for fuel
control and other functions such as idle, wide open
throttle, deceleration enleanment, and acceleration en-
richment.
Diagnostic Aids
If the idle is too high, stop the engine. Fully extend the main
throttle idle actuator (MTIA) with a IAC driver. Start the en-
gine. If the idle speed is above 800 rpm, locate and repair
the vacuum leak. Also, check for a binding throttle plate or
throttle linkage or an incorrect base idle setting.
Page 326 of 2643

1F – 80IENGINE CONTROLS
DAEWOO V–121 BL4
Idle Air Control System Check (1.4L/1.6L DOHC)
StepActionValue(s)YesNo
1Perform an On–Board Diagnostic (EOBD) System
Check.
Is the system check complete?–Go to Step 2Go to
”On–Board
Diagnostic Sys-
tem Check”
2Turn the ignition switch to ON.
Is the Malfunction Indicator Lamp (MIL) on steady?–Go to Step 4Go to Step 3
3Turn the ignition switch to LOCK.
Connect the scan tool to the DLC.
Turn the Turn the ignition switch to ON.
Are any diagnostic trouble codes (DTCs) displayed?–Go to Step 4Try with
another scan
tool
4Refer to the applicable DTC table.
Is only one DTC identified as valid trouble code
P0122?–Go to Step 5Go to
applicable DTC
table And go to
”Multiple DTC”
51. 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 6
61. Turn the ignition switch to lock.
2. Disconnect the MTIA connector.
3. Measure the voltage between terminal 2 and 8.
Does the voltage measure within the value speci-
fied?4.8V–5.0VGo to Step 7Go to Step 8
7Connect a fused jumper between the MTIA connec-
tor terminal 2 and terminal 7.
Does the scan tool show the TPS voltage above val-
ue specified?4.8V–5.0VGo to Step 13Go to Step 11
8Measure the voltage between the MTIA connector
2 and ground.
Does the voltage measure within the value speci-
fied?>5.0VGo to Step 9Go to Step 10
91. Turn the ignition switch to lock.
2. Check for an open or low voltage in the wire
between the MTIA connector 8 and ECM con-
nector 19.
Is the problem found?–Go to Step 12Go to Step 14
101. Turn the ignition switch to LOCK.
2. Check for an open or low voltage in the wire
between the MTIA connector 2 and ECM con-
nector 79.
Is the problem found?–Go to Step 12Go to Step 14
111. Turn the ignition switch to LOCK.
2. Check for an open or low voltage in the wire
between the MTIA connector 7 and ECM con-
nector 74.
Is the problem found?–Go to Step 12Go to Step 14
Page 327 of 2643
ENGINE CONTROLS 1F – 81
DAEWOO V–121 BL4
StepNo Yes Value(s) Action
121. 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–
131. Replace the throttle body assembly.
2. Clear any DTCs from ECM.
3. Perform the Diagnostic System Check.
Is the repair complete?–System OK–
141. Turn the ignition switch to LOCK.
2. Replace the ECM.
3. Perform the Diagnostic System Check.
Is the repair complete?–Go to Step 15–
15Check if any additional DTCs are set.
Are any DTCs displaced that have not been diag-
nosed?–Go to
applicable DTC
tableSystem OK
Page 328 of 2643

1F – 82IENGINE CONTROLS
DAEWOO V–121 BL4
IDLE AIR CONTROL SYSTEM CHECK (1.8L DOHC)
Circuit Description
The Engine Control Module (ECM) controls the engine idle
speed with the Idle Air Control (IAC) valve. To increase the
idle speed, the ECM pulls the IAC pintle away from its seat,
allowing more air to pass by the throttle body. To decrease
the idle speed, it extends the IAC valve pintle toward its
seat, reducing bypass air flow. A scan tool will read the
ECM commands to the IAC valve in counts. The higher
counts indicate more air bypass (higher idle). The lower
counts indicate less air is allowed to bypass (lower idle).
Diagnostic Aids
If the idle is too high, stop the engine. Fully extend the Idle
Air Control (IAC) valve with a IAC driver. Start the engine.
If the idle speed is above 800 rpm, locate and repair the
vacuum leak. Also, check for a binding throttle plate or
throttle linkage or an incorrect base idle setting.
Test Description
The number(s) below refer to step(s) on the diagnostic
table.
2. The IAC valve is extended and retracted by the IAC
driver. IAC valve movement is verified by an engine
speed change. If no change in engine speed oc-
curs, the valve can be removed from the throttle
body and tested. Connect the IAC driver to the re-
moved IAC valve and turn the ignition ON. Do not
start the engine.5. This step checks the quality of the IAC valve move-
ment in Step 2. Fully extending the IAC valve may
cause an engine stall. This may be normal.
6. Steps 2 and 5 verify proper IAC valve operation.
This step checks the IAC circuit for a wiring or ECM
fault.
Idle Air Control Valve Reset Procedure
Whenever the battery cable or the Engine Control Module
(ECM) connector or the ECM fuse Ef11 is disconnected or
replaced, the following idle learn procedure must be per-
formed:
1. Turn the ignition ON for 5 seconds.
2. Turn the ignition OFF for 10 seconds.
3. Turn the ignition ON for 5 seconds.
4. Start the engine in park/neutral.
5. Allow the engine to run until the engine coolant is
above 185°F (85°C).
6. Turn the A/C ON for 10 seconds, if equipped.
7. Turn the A/C OFF for 10 seconds, if equipped.
8. If the vehicle is equipped with an automatic trans-
axle, apply the parking brake. While pressing the
brake pedal, place the transaxle in D (drive).
9. Turn the A/C ON for 10 seconds, if equipped.
10. Turn the A/C OFF for 10 seconds, if equipped.
11. Turn the ignition OFF. The idle learn procedure is
complete.