ABS DAEWOO MATIZ 2003 Service Service Manual
[x] Cancel search | Manufacturer: DAEWOO, Model Year: 2003, Model line: MATIZ, Model: DAEWOO MATIZ 2003Pages: 1184, PDF Size: 36 MB
Page 284 of 1184
1F–186 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P1402 ELECTRIC EXHAUST GAS
RECIRCULATION BLOCKED
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A EEGR valve is used on this system. The linear EEGR
valve is designed to accurately supply exhaust gases to
the engine without the use of intake manifold vacuum.
The valve controls exhaust flow going into the intake
manifold from the exhaust manifold fhrough an orifice
with a engine control module(ECM) controlled pintle.
The ECM controls the pintle position using inputs from
the Throttle Position (TP) and the Manifold Absolute
Pressure (MAP) sensor. The ECM then commands the
EEGR valve to operate when necessary by controlling
an ignition signal through the ECM. This can be moni-
tored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.
Conditions for Setting the DTC
Engine Coolant Temperature(ECT) is greater than
80°C(176°F).Intake Air Temperature(IAT) is greater than 15°C
(59°F).
Manifold Absolute Pressure is greater than 75kPA.
The EEGR differential rate is less than 3%.
Mass Air Flow is between 92 ~157mg/tdc.
Engine Speed Is Between 2,500~2,900rpm.
DTCs P0107, P0108, P0112, P0113, P0117, P0118,
P0122, P0123, P0131, P0300, P0335, P0336,
P0341, P0342, P1671, P1672, P1673 are NOT SET.
EEGR is disabled.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) will illuminate.
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.
A history DTC is stored.
Conditions for Clearing the MIL/DTC
The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
Page 286 of 1184
1F–188 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P1403 ELECTRIC EXHAUST GAS
RECIRCULATION VALVE FAILURE
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.
Conditions for Setting THE DTC
Engine Coolant Temperature(ECT) is greater than
80°C(176°F).Intake Air Temperature(IAT) is greater than 15°C
(59°F).
Manifold Absolute Pressure is greater than 75kPA.
The open EEGR value is higher than 3%.
Mass Air Flow is between 92 ~157mg/tdc.
Engine Speed Is Between 2,500~2,900rpm.
EEGR potentiometer voltage is less than 0.4V.
EEGR potentiometer voltage is higher than 1.75V or
integral term of EEGR controller blocked in high or
low limit.
DTCs P0107, P0108, P0112, P0113, P0117, P0118,
P0122, P0123, P0131, P0300, P0335, P0336,
P0341, P0342, P1671, P1672, P1673 are NOT SET.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) will illuminate.
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.
A history DTC is stored.
Conditions for Clearing the MIL/DTC
The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
Page 290 of 1184
1F–192 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P0404 ELECTRIC EXHAUST GAS
RECIRCULATION OPENED
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC
EEGR circuit low voltage.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) will illuminate.
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.
A history DTC is stored.
EEGR is disabled.
Conditions for Clearing the MIL/DTC
The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).
Page 294 of 1184
1F–196 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P1404 ELECTRIC EXHAUST GAS
RECIRCULATION CLOSED
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC
EEGR circuit high voltage.
Action Taken When The DTCs Sets
The Malfunction Indicator Lamp (MIL) will illuminate.
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.
A history DTC is stored.
EEGR is disabled.
Conditions for Clearing the MIL/DTC
The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
DTC(s) can be cleared by using the scan tool.
Disconnecting the ECM battery feed for more than 10
seconds.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).
Page 298 of 1184
1F–200 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P0405 EEGR PINTLE POSITION
SENSOR LOW VOLTAGE
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
ThisDiagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC
EEGR voltage is less than 0.01V.
EEGR potentiometer circuit low voltage.
Action Taken When The DTCs Sets
The Malfunction Indicator Lamp (MIL) will illuminate.
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.
A history DTC is stored.
EEGR is disabled.
Conditions for Clearing the MIL/DTC
The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
DTC(s) can be cleared by using the scan tool.
Disconnecting the ECM battery feed for more than 10
seconds.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).
Page 302 of 1184
1F–204 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F230
DIAGNOSTIC TROUBLE CODE (DTC) – P0406 EEGR PINTLE POSITION
SENSOR HIGH VOLTAGE
Circuit Description
An Electric Exhaust Gas Re-circulation (EEGR) system
is used to lower oxides of nitrogen (NOX) emission lev-
els caused by high combustion temperatures. It a ac-
complishes this by feeding small amounts of exhaust
gases back into the combustion chamber. When the air/
fuel mixture is diluted with the exhaust gases, combus-
tion temperatures are reduced.
A linear EEGR valve is used on this system. The linear
EEGR valve is designed to accurately supply exhaust
gases to the engine without the use of intake manifold
vacuum. The valve controls exhaust flow going into the
intake manifold from the exhaust manifold fhrough an
orifice with a engine control module(ECM) controlled
pintle. The ECM controls the pintle position using inputs
from the Throttle Position (TP) and the Manifold Abso-
lute Pressure (MAP) sensor. The ECM then commands
the EEGR valve to operate when necessary by control-
ling an ignition signal through the ECM. This can be
monitored on a scan tool as the Desired EEGR position.
The ECM monitors the results of its command through a
feedback signal. By sending a 5 volt reference and a
ground to the EEGR valve, a voltage signal representing
the EEGR valve pintle position is sent to the ECM. This
feedback signal can also be monitored on a scan tool
and is the actual position of the EEGR pintle. The actual
EEGR position should always be near the commanded
or Desired EEGR position.
This Diagnostic Trouble Code(DTC) will detect an open
or short circuit.Conditions for Setting THE DTC
EEGR voltage is higher than 4.99V.
EEGR potentiometer circuit high voltage.
Action Taken When The DTCs Sets
The Malfunction Indicator Lamp (MIL) will illuminate.
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.
A history DTC is stored.
EEGR is disabled.
Conditions for Clearing the MIL/DTC
The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Due to moisture associated with exhaust systems, the
EEGR valve may freeze and stick in cold weather at
times. After the vehicle is brought into a warm shop for
repairs, the valve warms and the problem disappears.
By watching the Actual EEGR and desired EEGR posi-
tions on a cold vehicle with a scan tool, the fault can be
easily verified. Check the Freeze Frame data to deter-
mine if the DTC set when the vehicle was cold by view-
ing the Engine Coolant Temperature (ECT).
Page 344 of 1184
1F–246 ENGINE CONTROLS
DAEWOO M-150 BL2
MAA1F070
DIAGNOSTIC TROUBLE CODE (DTC) 0505
IDLE AIR CONTROL VALVE (IACV) CIRCUIT FAULT
Circuit Description
The Engine Control Module (ECM) controls the air en-
tering into the engine with an Idle Air Control (IAC)
Valve. To increase the idle rpm, the ECM commands the
pintle inside the IAC valve away from the throttle body
seat. This allows more air to bypass through the throttle
blade. To decrease the rpm the ECM commands the
pintle towards the throttle body seat. This reduces the
amount of air bypassing the throttle blade. A scan tool
will read the IAC valve pintle position in counts. The
higher the counts, the more air that is allowed to bypass
the throttle blade. This Diagnostic Trouble Code (DTC)
determines if a low idle condition exists as defined as
100 rpm below the desired idle rpm.
Conditions for Setting the DTC
No intrusive tests are active.
DTC(s) P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0131, P0132,
P0133, P1133, P1134, P0171, P1171, P0172, P0201,
P0202, P0203, P0204, P0300, P0336, P0337,
P0341, P0342, P0351, P0352, P0402, P0404,
P1404, P0405, P0406, P0443, and P0502 are not
set.
Engine is running more than 60 seconds.
Barometric Pressure (BARO) is greater than 72 kPa
(10.4 psi).
Engine Coolant Temperature (ECT) is greater than
60C (140F).
Ignition voltage is between 11 and 16 volts.
The Intake Air Temperature (IAT) is greater than
–20C (–4F).
Manifold Absolute Pressure is less than 60 kPa (8.7
psi).IAC valve is controlled fully opened.
All of the above must be met for greater than 5 sec-
onds.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) will illuminate.
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.
A history DTC is stored.
Conditions for Clearing the MIL/DTC
The MIL will turn off after four consecutive ignition
cycles in which the diagnostic runs without a fault.
A history DTC will clear after 40 consecutive warm-up
cycles without a fault.
DTC(s) can be cleared by using the scan tool.
Disconnecting the ECM battery feed for more than 10
seconds.
Diagnostic Aids
Inspect the IAC valve electrical connection for proper
mating.
Inspect the wiring harness for damage.
Inspect the throttle stop screw for signs of tampering.
Inspect the throttle linkage for signs of binding or exces-
sive wear.
A slow or unstable idle may be caused by one of the fol-
lowing conditions:
Fuel system too rich or too lean.
Foreign material in the throttle body bore or in the air
induction system.
A leaking or restricted intake manifold.
Page 381 of 1184
ENGINE CONTROLS 1F–283
DAEWOO M-150 BL2
HARD START
Definition: The engine cranks OK, but does not start for
a long time. The engine eventually runs or may start and
immediately die.Important: Ensure that the driver is using the correct
starting procedure. Before diagnosing, check service
bulletins for updates.
StepActionValue(s)YesNo
1
Were the Important Preliminary Checks performed?
–
Go to Step 2
Go to
“Important
Preliminary
Checks”
2
1. Connect the scan tool to the Data Link Connector
(DLC).
2. Check the Engine Coolant Temperature (ECT)
sensor and the Intake Air Temperature (IAT)
sensor using the scan tool.
3. Compare the coolant temperature and the IAT
with the ambient temperature when the engine is
cold.
Do the ECT and the IAT readings differ from the
ambient temperature by more than the value
specified?
3C (5F)Go to Step 3Go to Step 4
3
1. Measure the resistance of the ECT sensor and
the IAT sensor.
2. Compare the resistance value to specifications
using the Temperature Vs. Resistance tables for
DTCs P0118 and P0113.
3. If the resistance is not the same, replace the
faulty sensor.
Is the repair complete?
–
System OK
–
4
1. Check for a sticking throttle shaft or a binding
linkage that may cause a high Throttle Position
(TP) sensor voltage. Repair or replace as
needed.
2. Check the TP sensor voltage reading with the
throttle closed.
Does the voltage measure within the value
specified?
0.4–0.8 VGo to Step 5Go to Step 26
5
1. Check the Manifold Absolute Pressure (MAP)
sensor response and accuracy.
2. Replace the MAP sensor as needed.
Is the repair complete?
–
System OKGo to Step 6
6
Check the fuel pump operation.
Does the fuel pump operate for the specified time
when the ignition switch is turned ON?
2 secGo to Step 7
Go to “Fuel
Pump Relay
Circuit Check”
7Check the fuel system pressure.
Is the fuel pressure within the specifications?380 kPa
(55 psi)
Go to Step 8Go to Step 27
8Check for water contamination in the fuel.
Is fuel contaminated?–Go to Step 9Go to Step 10
9Replace the contaminated fuel.
Is the repair complete?–System OK–
Page 390 of 1184
1F–292 ENGINE CONTROLS
DAEWOO M-150 BL2
HESITATION, SAG, STUMBLE
Definition: Momentary lack of response as the accelera-
tor is pushed down. This can occur at any vehicle speed.
It is usually the most severe when first trying to make the
vehicle move, as from a stop. Hesitation, sag, or
stumble may cause the engine to stall if severe enough.Important: Before diagnosing this condition, check ser-
vice bulletins for PROM updates.
StepActionValue(s)YesNo
1
Were the Important Preliminary Checks performed?
–
Go to Step 2
Go to
“Important
Preliminary
Checks”
2
1. Check the fuel system pressure. If the pressure is
not within the value specified, service the fuel
system as needed.
2. Inspect the Throttle Position (TP) sensor for
binding or sticking. The TP sensor voltage should
increase at a steady rate as the throttle is moved
toward Wide Open Throttle (WOT).
Is the problem found?
380 kPa
(55 psi)
Go to Step 3Go to Step 4
3Repair or replace any components as needed.
Is the repair complete?–System OK–
4
1. Check the Manifold Absolute Pressure (MAP)
sensor response and accuracy.
2. Inspect the fuel for water contamination.
3. Check the Evaporative Emission (EVAP) Canister
Purge System for proper operation.
Is the problem found?
–
Go to Step 5Go to Step 6
5Repair or replace any components as needed.
Is the repair complete?–System OK–
6
1. Disconnect all of the fuel injector harness
connectors.
2. Connect an injector test light between the
harness terminals of each fuel injector.
3. Note the test light while cranking the engine.
Does the test light blink on all connectors?
–
Go to Step 8Go to Step 7
7
1. Repair or replace the faulty fuel injector drive
harness, the connector, or the connector terminal.
2. If the connections and the harnesses are good,
replace the Engine Control Module (ECM).
Is the repair complete?
–
System OK
–
8
Measure the resistance of each fuel injector.
Is the fuel injector resistance within the value
specified (the resistance will increase slightly at
higher temperatures)?
11.6–12.4 ΩGo to Step 10Go to Step 9
9
Replace any of the fuel injectors with a resistance
that is out of specifications.
Is the repair complete?
–
System OK
–
10Perform an injector diagnosis.
Is the problem found?–Go to Step 11Go to Step 12
11Replace any restricted or leaking fuel injectors.
Is the repair complete?–System OK–
12
Check the fuel system pressure after a cold start or
during moderate or full throttle acceleration.
Is the fuel pressure within specifications?
380 kPa
(55 psi)
Go to Step 14Go to Step 13
Page 395 of 1184
ENGINE CONTROLS 1F–297
DAEWOO M-150 BL2
ROUGH, UNSTABLE, OR INCORRECT IDLE, STALLING
Definition: The engine runs unevenly at idle. If the condi-
tion is bad enough, the vehicle may shake. Also, the idle
varies in rpm (called “hunting”). Either condition may be
severe enough to cause stalling. The engine idles at in-
correct idle speed.Important: Before diagnosing the symptom, check ser-
vice bulletins for updates.
StepActionValue(s)YesNo
1
Were the Important Preliminary Checks performed?
–
Go to Step 2
Go to
“Important
Preliminary
Checks”
2
1. Connect the scan tool to the Data Link Connector
(DLC).
2. Monitor the oxygen sensor (O2S) reading at
different throttle positions.
Does the O2S change quickly from rich to lean at
the different throttle positions?
–
Go to Step 5Go to Step 3
3
Check the O2S for contamination from fuel or
improper use of room temperature vulcanizing
sealant.
Is the O2S contaminated?
–
Go to Step 4Go to Step 5
4Replace the contaminated O2S as needed.
Is the repair complete?–System OK–
5
1. Check for a sticking throttle shaft or binding
throttle linkage that may cause incorrect Throttle
Position (TP) sensor voltage.
2. Check the TP sensor voltage reading with the
throttle closed.
Is the TP sensor voltage within the value specified?
0.4–0.8 VGo to Step 6
Go to
“Diagnostic
Aids for DTC
P0123”
6
1. Check the Engine Coolant Temperature (ECT)
sensor voltage reading using the scan tool.
2. Compare the ECT sensor reading with the
ambient temperature when the engine is cold.
Does the ECT sensor temperature reading differ
from the ambient temperature by more than the
value specified?
3C (5F)Go to Step 7Go to Step 9
7
Check for high resistance in the ECT sensor circuit
or the sensor itself.
Is the problem found?
–
Go to Step 8Go to Step 9
8
Replace the ECT sensor or repair the circuit as
needed.
Is the repair complete?
–
System OK
–
9
Check the Manifold Absolute Pressure (MAP)
sensor for response and accuracy.
Is the problem found?
–
Go to Step 10Go to Step 11
10
Replace the MAP sensor or repair the MAP sensor
circuit as needed.
Is the repair complete?
–
System OK
–
11
1. Road test the vehicle at the speed of the
complaint.
2. Monitor the long term fuel trim reading using the
scan tool.
Is the long term fuel trim reading within the value
specified?
–20–25%Go to Step 14Go to Step 12