Daewoo CIELO EURO III, Manual

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1F – 189 ENGINE CONTROLS
DAEWOO T-154 BL2,3
DIAGNOSTIC TROUBLE CODE (DTC) P0171
FUEL TRIM SYSTEM TOO LEAN
System Description
To provide the best possible combination of driveability,
fuel economy, and emission control, a Closed Loop air/
fuel metering system is used. While in Closed Loop, the
engine control module
(ECM) monitors the oxygen sensor (O2S 1) signal volt-
age and adjusts fuel delivery based on signal voltage. A
change made to fuel delivery will be indicated by the
long and short term fuel trim values which can be moni-
tored with the scan tool. Ideal fuel trim values are around
128 (0%). If the O2S 1 signal is indicating a lean condi-
tion, the ECM will add fuel resulting in fuel trim val-
ues above 128 (0% to 100%). If a rich condition is
detected, the fuel trim values will be below 128 (0% to
–100%), indicating that the ECM is reducing the
amount of fuel delivered. If exhaust emissions reach an
excessive level due to a lean or rich condition, a fuel trim
Diagnostic Trouble Code (DTC) is set.
Conditions for Setting the DTC
No intrusive tests active.
The Intake Air Temperature (IAT) is between –40
q
C
(–40
q
F) and 120
q
C (248
q
F).
The system is in Closed Loop (C/L).
The adaptive index ready.
1.5L SOHC
The average of short term fuel trim values is greater
than or equal to 0.94 and the average of adaptive in-
dex multiplier values is greater than or equal to 1.28.
DTC(s) P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, P0125, P0131,
P0132, P0133, P0134, P0300, P0336, P0337,
P0341, P0342, P0402, P0404, P0405, P0406,
P0443, P0506, P0507, P1167, P1171 and P1404 are
not set.
The Throttle position (TP) is less than 80%.
The engine speed is between 700 and 6000 rpm.
The Barometric Pressure (BARO) is greater than
72.0 kPa.
The coolant temperature is between 70
q
C (158
q
F)
and 105
q
C (221
q
F).
The vehicle speed is less than 87 mph (140 km/h).
The system voltage is greater than 11 volts.
The airflow is between 1.5 and 45 g/sec.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) will illuminate
after two consecutive ignitions in which the diagnostic
runs with the fault active.
The ECM will record operating conditions at the
time the diagnostic fails. This information will be
stored in the Freeze Frame and Failure Records buff-
ers.
A history DTC is stored.
Conditions for Clearing the MIL/DTC
The MIL will turn off after three (four –
1.5L SOHC) consecutive ignition cycles in which the
diagnostic runs without a fault within the freeze frame
conditions that the DTC failed.
A history DTC will clear after 40 consecutive warm up
cycles without a fault.
The DTC(s) can be cleared by using the scan tool.
Diagnostic Aids
Important: After repairs, use the scan tool Fuel Trim
Reset function to reset the long term fuel trim to
128 (0%).
Fuel pressure – The system will be lean if the pressure
is too low. It may be necessary to monitor fuel pressure
while driving the vehicle at various road speeds and/or
loads to confirm.
Map sensor – An output that causes the ECM to
sense a lower than normal manifold pressure (high vac-
uum) can cause the system to go lean. Disconnecting
the MAP sensor will allow the ECM to substitute a
fixed (default) value for the MAP sensor. If the lean con-
dition is gone when the sensor is disconnected, substi-
tute a known good sensor and recheck.
Fuel contamination – Water, in even small amounts,
near the in-tank fuel pump inlet, can be delivered to the