Common Eobd Terms - Daewoo CIELO EURO III Manual

1F – 418 ENGINE CONTROLS
Refer to ECM and Sensors in General Descrip-
tions.
Passive and Active Diagnostic Tests
A passive test is a diagnostic test which simply monitors
a vehicle system or component. Conversely, an active
test, actually takes some sort of action when performing
diagnostic functions, often in response to a failed pas-
sive test. For example, the Exhaust Gas Recirculation
(EGR) diagnostic active test will force the EGR valve
open during closed throttle deceleration and/or force the
EGR valve closed during a steady state. Either action
should result in a change in manifold pressure.
Intrusive Diagnostic Tests
This is any on-board test run by the Diagnostic Manage-
ment System which may have an effect on vehicle per-
formance or emission levels.
Warm-Up Cycle
A warm-up cycle means that engine at temperature
must reach a minimum of 70_C (160_F) and rise at least
22_C (40_F) over the course of a trip.
Freeze Frame
Freeze Frame is an element of the Diagnostic Manage-
ment System which stores various vehicle information at
the moment an emissions-related fault is stored in
memory and when the Malfunction Indicator Lamp (MIL)
is commanded on. These data can help to identify the
cause of a fault.
Failure Records
Failure Records data is an enhancement of the EOBD
Freeze Frame feature. Failure Records store the same
vehicle information as does Freeze Frame, but it will
store that information for any fault which is stored in on-
board memory, while Freeze Frame stores information
only for emission-related faults that command the MIL
on.

COMMON EOBD TERMS

Diagnostic
When used as a noun, the word diagnostic refers to any
on-board test run by the vehicle's Diagnostic Manage-
ment System. A diagnostic is simply a test run on a sys-
tem or component to determine if the system or
component is operating according to specification.
There are many diagnostics, shown in the following list:
D Misfire
D Oxygen sensors (O2S 1)
D Oxygen sensor (HO2S 2)
D Exhaust Gas Recirculation (EGR)
D Catalyst monitoring
Enable Criteria
The term "enable criteria" is engineering language for
the conditions necessary for a given diagnostic test to
run. Each diagnostic has a specific list of conditions
which must be met before the diagnostic will run.
"Enable criteria" is another way of saying "conditions re-
quired".
The enable criteria for each diagnostic is listed on the
first page of the DTC description under the heading
"Conditions for Setting the DTC." Enable criteria varies
with each diagnostic, and typically includes, but is not
limited to the following items:
D Engine speed
D Vehicle speed
D Engine Coolant Temperature (ECT)
D Manifold Absolute Pressure (MAP)
D Barometric Pressure (BARO)
D Intake Air Temperature (IAT)
D Throttle Position (TP)
D High canister purge
D Fuel trim
D A/C on
Trip
Technically, a trip is a key-on run key-off cycle in which
all the enable criteria for a given diagnostic are met, al-
lowing the diagnostic to run. Unfortunately, this concept
is not quite that simple. A trip is official when all the en-
able criteria for a given diagnostic are met. But because
the enable criteria vary from one diagnostic to another,
the definition of trip varies as well. Some diagnostics are
run when the vehicle is at operating temperature, some
when the vehicle first start up; some require that the ve-
hicle be cruising at a steady highway speed, some run
only when the vehicle is at idle;
Some run only immediately following a cold engine start-
up.
A trip then, is defined as a key on-run-key off cycle in
which the vehicle was operated in such a way as to sat-
isfy the enables criteria for a given diagnostic, and this
diagnostic will consider this cycle to be one trip. Howev-
er, another diagnostic with a different set of enable crite-
ria (which were not met) during this driving event, would
not consider it a trip. No trip will occur for that particular
diagnostic until the vehicle is driven in such a way as to
meet all the enable criteria
Diagnostic Information
The diagnostic charts and functional checks are de-
signed to locate a faulty circuit or component through a
process of logical decisions. The charts are prepared
with the requirement that the vehicle functioned correct-
ly at the time of assembly and that there are not multiple
faults present.
There is a continuous self–diagnosis on certain control
functions. This diagnostic capability is complimented by
the diagnostic procedures contained in this manual. The
language of communicating the source of the malfunc-
DAEWOO T-154 BL2,3