Daewoo CIELO EURO III, Manual

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ENGINE CONTROLS 1F – 148
DAEWOO T-154 BL2,3
speeds and/or loads to confirm. Refer to “Fuel System
Diagnosis” in this section.
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
injector. The water causes a lean exhaust and can set
DTC P0131.
Sensor harness – The O2S 1 sensor pigtail may be mis-
positioned and contacting the exhaust manifold.
Engine misfire – A misfiring cylinder will result in un-
burned oxygen in the exhaust, which could cause DTC
P0131 to set. Refer to “DTC P0300 Multiple Cylinder
Misfire Detected” in this section.
Cracked Oxygen Sensor (O2S 1) – A cracked O2S 1 or
poor ground at the sensor could cause a DTC P0131.
Refer to Symptoms.
Plugged fuel filter – A plugged fuel filter can cause a lean
condition and cause a DTC P0131 to set.
Plugged Oxygen Sensor (O2S 1) – A plugged reference
port on the Oxygen Sensor (O2S 1) will indicate a lower
than normal voltage output from the O2S 1.
Test Description
Number(s) below refer to the step number(s) on the
Diagnostic 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. This step determines if DTC P0131 is the result of a
hard failure or an intermittent condition. It may be
necessary to operate the vehicle within the Freeze
Frame conditions and Conditions for Setting the
DTC in order to duplicate the malfunction detected
by the ECM.
4. This step simulates DTC P0134. If the ECM
senses the change, the ECM and the wiring
are OK.
6. The replacement ECM must be repro-
grammed. Refer to the latest Techline procedure for
ECM reprogramming.
8. If no malfunctions have been found at this point and
no additional DTCs were set, refer to “Diagnostic
Aids” for additional checks and information.
DTC P0131 Oxygen Sensor (O2S 1) Low Voltage
Step Action Value Yes No
1
Perform an On-Board Diagnostic (EOBD) System
Check.
Is the system check complete?
–
Go to Step 2
Go to
“On-Board
Diagnostic
System Check”
2
1. Turn the ignition ON, with the engine OFF.
2. Install a scan tool.
3. Engine at operating temperature.
Does the Oxygen Sensor (O2S 1) voltage remain
below the specified value?
100 mv Go to Step 4 Go to Step 3
3
1. Review the Freeze Frame data and note the
parameters.
2. Operate the vehicle within the Freeze Frame
conditions and Conditions For Setting The DTC
as noted?
Does the O2S 1 voltage stay below the specified
value?
100 mv Go to Step 4 Go to Step 7
4
1. Turn the ignition switch ON, with the engine OFF.
2. Disconnect the O2S 1 electrical connector.
Does the scan tool indicate the O2S 1 voltage within
the specified values?
407-509 mv
Go to “Diagnos-
tic Aids” Go to Step 5
5
Check the O2S 1 sensor signal circuit, terminal 2 for
a short to ground and repair as necessary.
Is a repair necessary.
–
Go to Step 7 Go to Step 6