Daewoo NUBIRA, User Manual

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ENGINE CONTROLS 1F – 413
DAEWOO V–121 BL4
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It informs the driver that a fault that affects vehicle
emission levels has occurred and that the vehicle
should be taken for service as soon as possible.
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As a system check, the MIL will come on with the
key ON and the engine not running. When the en-
gine is started, the MIL will turn OFF.
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When the MIL remains ON while the engine is run-
ning, or when a malfunction is suspected due to a
driveability or emissions problem, an OBD II Sys-
tem Check must be performed. The procedures for
these checks are given in OBD II System Check.
These checks will expose faults which may not be
detected if other diagnostics are performed first.
Data Link Connector (DLC)
The provision for communicating with the control module
is the Data Link Connector (DLC). The DLC is used to con-
nect to a scan tool. Some common uses of the scan tool
are listed below:
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Identifying stored DTCs.
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Clearing DTCs.
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Performing output control tests.
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Reading serial data.
DTC TYPES
Each Diagnostic Trouble Code (DTC) is directly related to
a diagnostic test. The Diagnostic Management System
sets DTC based on the failure of the tests during a trip or
trips. Certain tests must fail two consecutive trips before
the DTC is set. The following are the three types of DTCs
and the characteristics of those codes:
Type A
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Emissions related.
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Requests illumination of the Malfunction Indicator
Lamp (MIL) of the first trip with a fail.
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Stores a History DTC on the first trip with a fail.
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Stores a Freeze Frame (if empty).
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Stores a Fail Record.
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Updates the Fail Record each time the diagnostic
test fails.
Type B
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Emissions related.
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”Armed” after one trip with a fail.
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”Disarmed” after one trip with a pass.
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Requests illumination of the MIL on the second
consecutive trip with a fail.
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Stores a History DTC on the second consecutive
trip with a fail (The DTC will be armed after the first
fail).
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Stores a Freeze Frame on the second consecutive
trip with a fail (if empty).
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Store Fail Record when the first test fails (not de-
pendent on consecutive trip fails).
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Updates the Fail Record each time the diagnostic
test fails.
Type D
(Type D non–emissions related are not utilized on certain
vehicle applications).
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Non–Emissions related.
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Does not request illumination of any lamp.
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Stores a History DTC on the first trip with a fail.
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Does not store a Freeze Frame.
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Stores Fail Record when test fails.
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Updates the Fail Record each time the diagnostic
test fails.
Important : Only four Fail Records can be stored. Each
Fail Record is for a different DTC. It is possible that there
will not be Fail Records for every DTC if multiple DTCs are
set.
Special Cases of Type B Diagnostic Tests
Unique to the misfire diagnostic, the Diagnostic Executive
has the capability of alerting the vehicle operator to poten-
tially damaging levels of misfire. If a misfire condition ex-
ists that could potentially damage the catalytic converter
as a result of high misfire levels, the Diagnostic Executive
will command the MIL to flash at a rate of once per second
during those the time that the catalyst damaging misfire
condition is present.
Fuel trim and misfire are special cases of Type B diagnos-
tics. Each time a fuel trim or misfire malfunction is de-
tected, engine load, engine speed, and engine coolant
temperature (ECT) are recorded.
When the ignition is turned off, the last reported set of con-
ditions remain stored. During subsequent ignition cycles,
the stored conditions are used as a reference for similar
conditions. If a malfunction occurs during two consecutive
trips, the Diagnostic Executive treats the failure as a nor-
mal Type B diagnostic, and does not use the stored condi-
tions. However, if a malfunction occurs on two non–con-
secutive trips, the stored conditions are compared with the
current conditions. The MIL will then illuminate under the
following conditions:
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When the engine load conditions are within 10% of
the previous test that failed.
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Engine speed is within 375 rpm of the previous test
that failed.
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ECT is in the same range as the previous test that
failed.
READING DIAGNOSTIC TROUBLE
CODES
The procedure for reading diagnostic trouble code(s) is to
use a diagnostic scan tool. When reading Diagnostic
Trouble Codes (DTCs), follow the instructions supplied by
tool manufacturer.
Clearing Diagnostic Trouble Codes
Important : Do not clear DTCs unless directed to do so
by the service information provided for each diagnostic
procedure. When DTCs are cleared, the Freeze Frame