Daewoo CIELO EURO III, Manual

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1F – 4 1 6 ENGINE CONTROLS
DAEWOO T-154 BL2,3
D
If a Diagnostic Trouble Code (DTC) was diagnosed,
verify a repair by duplicating conditions present when
the DTC was set as noted in the Failure Records or
Freeze Frame data.
Verifying Vehicle Repair
Verification of the vehicle repair will be more compre-
hensive for vehicles with On-Board Diagnostic (EOBD)
system diagnostics. Following a repair, the technician
should perform the following steps:
Important: Follow the steps below when you verify re-
pairs on EOBD systems. Failure to follow these steps
could result in unnecessary repairs.
D
Review and record the Failure Records and the
Freeze Frame data for the DTC which has been diag-
nosed (Freeze Fame data will only be stored for an A
or B type diagnostic and only if the Malfunction Indi-
cator Lamp has been requested).
D
Clear the DTC(s).
D
Operate the vehicle within conditions noted in the
Failure Records and Freeze Frame data.
D
Monitor the DTC status information for the specific
DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.
EOBD SERVICEABILITY ISSUES
Based on the knowledge gained from On-Board Diag-
nostic (EOBD) experience, this list of non-vehicle faults
that could affect the performance of the EOBD system
has been compiled. These non-vehicle faults vary from
environmental conditions to the quality of fuel used. With
the introduction of EOBD across the entire passenger
car and light-duty truck market, illumination of the Mal-
function Indicator Lamp (MIL) due to a non-vehicle fault
could lead to misdiagnosis of the vehicle, increased war-
ranty expense and customer dissatisfaction. The follow-
ing list of non-vehicle faults does not include every
possible fault and may not apply equally to all product
lines.
Fuel Quality
Fuel quality is not a new issue for the automotive indus-
try, but its potential for turning on the MIL with EOBD
systems is new.
Fuel additives such as “dry gas” and “octane enhancers”
may affect the performance of the fuel. If this results in
an incomplete combustion or a partial burn, it will set
DTC P0300. The Reed Vapor Pressure of the fuel can
also create problems in the fuel system, especially dur-
ing the spring and fall months when severe ambient
temperature swings occur. A high Reed Vapor Pressure
could show up as a Fuel Trim DTC due to excessive
canister loading. High vapor pressures generated in the
fuel tank can also affect the Evaporative Emission diag-
nostic as well.
Using fuel with the wrong octane rating for your vehicle
may cause driveability problems. Many of the major fuel
companies advertise that using “premium” gasoline will
improve the performance of your vehicle. Most premium
fuels use alcohol to increase the octane rating of the
fuel. Although alcohol–enhanced fuels may raise the oc-
tane rating, the fuel’s ability to turn into vapor in cold
temperatures deteriorates. This may affect the starting
ability and cold driveability of the engine.
Low fuel levels can lead to fuel starvation, lean engine
operation, and eventually engine misfire.
Non–OEM Parts
All the EOBD parts have been calibrated to run with
Original Equipment Manufacturer (OEM) parts. Some-
thing as simple as a high performance-exhaust system
that affects exhaust system back pressure could poten-
tially interfere with the operation of the Exhaust Gas Re-
circulation (EGR) valve and thereby turn on the MIL.
Small leaks in the exhaust system near the post catalyst
oxygen sensor can also cause the MIL to turn on.
Aftermarket electronics, such as cellular phones, ster-
eos, and anti-theft devices, may radiate Electromagnet-
ic Interference (EMI) into the control system if they are
improperly installed. This may cause a false sensor
reading and turn on the MIL.
Environment
Temporary environmental conditions, such as localized
flooding, will have an effect on the vehicle ignition sys-
tem. If the ignition system is rain-soaked, it can tempo-
rarily cause engine misfire and turn on the MIL.
Vehicle Marshaling
The transportation of new vehicles from the assembly
plant to the dealership can involve as many as 60 key
cycles within 2 to 3 miles of driving. This type of opera-
tion contributes to the fuel fouling of the spark plugs and
will turn on the MIL with a set DTC P0300.
Poor Vehicle Maintenance
The sensitivity of the EOBD will cause the MIL to turn on
if the vehicle is not maintained properly. Restricted air fil-
ters, fuel filters, and crankcase deposits due to lack of oil
changes or improper oil viscosity can trigger actual ve-
hicle faults that were not previously monitored prior to
EOBD. Poor vehicle maintenance can not be classified
as a “non-vehicle fault”, but with the sensitivity of the
EOBD, vehicle maintenance schedules must be more
closely followed.
Severe Vibration
The Misfire diagnostic measures small changes in the
rotational speed of the crankshaft. Severe driveline
vibrations in the vehicle, such as caused by an exces-
sive amount of mud on the wheels, can have the same
effect on crankshaft speed as misfire and therefore may
set DTC P0300.