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1F – 195 ENGINE CONTROLS
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 less than
or equal to 1.06 and the average of adaptive index
multiplier values is less than or equal to 0.72.
DTC(s) P0106, P0107, P0108, P0112, P0113,
P0117, P0118, P0122, P0123, 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 50 q C (122 q F)
and 125 q C (257 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.
The Manifold Air Pressure (MAP) is between 25 and
90 kPa.
DIAGNOSTIC TROUBLE CODE (DTC) P0172
FUEL TRIM SYSTEM TOO RICH
.
Action Taken When the DTC Sets
The Malfunction Indicator Lamp (MIL) will illuminate
after three (1.5L SOHC)
consecutive trip with a fail.
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%).
Check for poor connection at the ECM. Inspect the
harness connectors for the following conditions:
Backed-out terminals
Improper mating
Broken locks
Improperly formed
Damaged terminals
Poor terminal to wire connection
Inspect the wiring harness for damage. If the harness
appears to be OK, observe the O2S 1 display on the
scan tool while moving the connectors and the wiring
DAEWOO T-154 BL2,3
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