Input Components; Output Components; Passive And Active Diagnosis Tests; Intrusive Diagnosis Tests - Isuzu C22NE Workshop Manual

6E1-46 DRIVEABILITY AND EMISSIONS

Input Components:

Input components are monitored for circuit continuity
and out-of-range values. This includes rationality
checking. Rationality checking refers to indicating a
fault when the signal from a sensor does not seem
reasonable, i.e. Throttle Position (TP) sensor that
indicates high throttle position at low engine loads or
MAP voltage). Input components may include, but are
not limited to the following sensors:
• Vehicle Speed Sensor (VSS)
• Crankshaft Position (CKP) sensor
• Throttle Position (TP) sensor
• Engine Coolant Temperature (ECT) sensor
• Intake Air Temperature Sensor (IAT)
• Manifold Absolute Pressure (MAP) sensor
In addition to the circuit continuity and rationality check
the ECT sensor is monitored for its ability to achieve a
steady state temperature to enable "Closed Loop" fuel
control (If applicable).

Output Components:

Output components are
response to control module commands. Components
where functional monitoring is not feasible will be
monitored for circuit continuity and out-of-range values
if applicable.
Output components to be monitored include, but are
not limited to the following circuit:
• Idle Air Control (IAC) Motor
• EVAP Canister Purge Valve Solenoid
• A/C relays
• VSS output
• MIL control
Refer to ECM and Sensors in General Descriptions.
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 passive test.
Intrusive Diagnostic Tests
This is any on-board test run by the Diagnostic
Management System which may have an effect on
vehicle performance 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.
diagnosed for proper

COMMON OBD TERMS

Diagnostic For Closed Loop System:

When used as a noun, the word diagnostic refers to
any on-board test run by the vehicle's Diagnostic
Management System. A diagnostic is simply a test run
on a system or component to determine if the system
or component is operating according to specification.
For Closed Loop System:
There are many diagnostics, shown in the following
list:
• Oxygen sensors
• Oxygen sensor heaters

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
required" .
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:
• engine speed
• vehicle speed
• ECT
• MAP
• IAT
• TP
• high canister purge (If applicable)
• 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, allowing the diagnostic to run. Unfortunately, this
concept is not quite that simple. A trip is official when
all the enable 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 vehicle 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