Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1239

6E1–32

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Maintenance Schedule

Refer to the Maintenance Schedule.

Visual/Physical Engine Compartment
Inspection

Perform a careful visual and physical engine
compartment inspection when performing any diagnostic
procedure or diagnosing the cause of an emission test
failure. This can often lead to repairing a problem without
further steps. Use the following guidelines when
performing a visual/physical inspection:

Inspect all vacuum hoses for pinches, cuts,
disconnection, and Droper routing.

Inspect hoses that are difficult to see behind other
components.

Inspect all wires in the engine compartment for proper
connections, burned or chafed spots, pinched wires,
contact with sharp edges or contact with hot exhaust
manifolds or pipes.

Basic Knowledge Of Tools Required

NOTE: Lack of basic knowledge of this powertrain when
performing diagnostic procedures could result in an
incorrect diagnosis or damage to powertrain
components. Do not attempt to diagnose a powertrain
problem without this basic knowledge.

A basic understanding of hand tools is necessary to
effectively use this section of the Service Manual.

SERIAL DATA COMMUNICATIONS

Class II Serial Data Communications

Government regulations require that all vehicle
manufacturers establish a common communication
system. This vehicle utilizes the ”Class II” communication
system. Each bit of information can have one of two
lengths: long or short. This allows vehicle wiring to be
reduced by transmitting and receiving multiple signals
over a single wire. The messages carried on Class II data
streams are also prioritized. If two messages attempt to
establish communications on the data line at the same
time, only the message with higher priority will continue.
The device with the lower priority message must wait. The
most significant result of this regulation is that it provides
Tech 2 manufacturers with the capability to access data
from any make or model vehicle that is sold.
The data displayed on the other Tech 2 will appear the
same, with some exceptions. Some Scan Tools will only
be able to display certain vehicle parameters as values
that are a coded representation of the true or actual value.
For more information on this system of coding, refer to
Decimal/Binary/Hexadecimal Conversions. On this
vehicle the Tech 2 displays the actual values for vehicle
parameters. It will not be necessary to perform any
conversions from coded values to actual values.

ON–BOARD

DIAGNOSTIC (OBD II)

On–Board Diagnostic Tests

A diagnostic test is a series of steps, the result of which is
a pass or fail reported to the diagnostic executive. When a
diagnostic test reports a pass result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The diagnostic test has passed during the current
ignition cycle.

The fault identified by the diagnostic test is not
currently active.

When a diagnostic test reports a fail result, the diagnostic
executive records the following data:

The diagnostic test has been completed since the last
ignition cycle.

The fault identified by the diagnostic test is currently
active.

The fault has been active during this ignition cycle.

The operating conditions at the time of the failure.

Remember, a fuel trim DTC may be triggered by a list of
vehicle faults. Make use of all information available (other
DTCs stored, rich or lean condition, etc.) when
diagnosing a fuel trim fault.

Comprehensive Component Monitor
Diagnostic Operation

Comprehensive component monitoring diagnostics are
required to monitor emissions–related input and output
powertrain components. The

CARB OBD II

Comprehensive Component Monitoring List Of
Components Intended To illuminate The MIL is a list of
components, features or functions that could fall under
this requirement.

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

Camshaft Position (CMP) sensor

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.

6E1–33

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

Output Components:
Output components are diagnosed for proper 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

Cooling fan relay(s)

VSS output

MIL control

Cruise control inhibit

Refer to PCM 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. For example, the EGR diagnostic active test will
force the EGR valve open during closed throttle decel
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
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

(40

F) over the course of a trip.

Freeze Frame
Freeze Frame is an element of the Diagnostic
Management System which stores various vehicle
information at the moment an emissions–related fault is
stored in memory and when the MIL is commanded on.
These data can help to identify the cause of a fault. Refer
to Storing And Erasing Freeze Fame Data for more
detailed information.

Failure Records
Failure Records data is an enhancement of the OBD II
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.

System Status And Drive Cycle For
Satisfying Federal
Inspection/Maintenance (I/M 240)
Regulations

I/M Ready Status means a signal or flag for each
emission system test that had been set in the PCM. I/M
Ready Status indicates that the vehicle on–board
emissions diagnostics have been run. I/M Ready Status
is not concerned whether the emission system passed or
failed the test, only that on–board diagnosis is complete.
Not all vehicles use all possible I/M flags.

Common OBD II Terms

Diagnostic
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. There
are many diagnostics, shown in the following list:

Misfire

Oxygen sensors

Oxygen sensor heaters

EGR

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 required”.
The enable criteria for each diagnostic is listed on the first
page of the DTC description in Section 6E1 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

barometric pressure

IAT

high canister purge

fuel trim

A/C ON

6E1–34

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

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 starts up; some require that the vehicle be
cruising at a steady highway speed, some run only when
the vehicle is at idle; some diagnostics function with the
TCC disabled. 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 satisfy
the enabling criteria for a given diagnostic, and this
diagnostic will consider this cycle to be one trip. However,
another diagnostic with a different set of enable criteria
(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.

The Diagnostic Executive

The Diagnostic Executive is a unique segment of
software which is designed to coordinate and prioritize
the diagnostic procedures as well as define the protocol
for recording and displaying their results. The main
responsibilities of the Diagnostic Executive are listed as
follows:

Commanding the MIL (”Check Engine” lamp) ON and
OFF

DTC logging and clearing

Freeze Frame data for the first emission related DTC
recorded

Non–emission related Service Lamp (future)

Operating conditions Failure Records buffer, (the
number of records will vary)

Current status information on each diagnostic

System Status (I/M ready)

The Diagnostic Executive records DTCs and turns ON
the MIL when emission–related faults occur. It can also
turn OFF the MIL if the conditions cease which caused the
DTC to set.

Diagnostic Information
The diagnostic charts and functional checks are designed
to locate a faulty circuit or component through a process
of logical decisions. The charts are prepared with the
requirement that the vehicle functioned correctly at the
time of assembly and that there are no 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 malfunction
is a system of diagnostic trouble codes. When a
malfunction is detected by the control module, a
diagnostic trouble code is set and the Malfunction
Indicator Lamp (MIL) (”Check Engine” lamp) is
illuminated.

Malfunction Indicator Lamp (MIL)
The Malfunction Indicator Lamp (MIL) looks the same as
the MIL you are already familiar with (”Check Engine”
lamp). However, OBD II requires that it illuminate under a
strict set of guide lines.
Basically, the MIL is turned ON when the PCM detects a
DTC that will impact the vehicle emissions.
The MIL is under the control of the Diagnostic Executive.
The MIL will be turned ON if an emissions–related
diagnostic test indicates a malfunction has occurred. It
will stay ON until the system or component passes the
same test, for three consecutive trips, with no
emissions–related faults.
If the vehicle is experiencing a misfire malfunction which
may cause damage to the Three–Way Catalytic
Converter (TWC), the MIL will flash once per second.
This will continue until the vehicle is outside of speed and
load conditions which could cause possible catalyst
damage, and the MIL will stop flashing and remain ON
steady.

Extinguishing the MIL
When the MIL is ON, the Diagnostic Executive will turn
OFF the MIL after

three (3) consecutive trips that a ”test

passed” has been reported for the diagnostic test that
originally caused the MIL to illuminate.
Although the MIL has been turned OFF, the DTC will
remain in the PCM memory (both Freeze Frame and
Failure Records) until

forty(40) warm–up cycles after no

faults have been completed.
If the MIL was set by either a fuel trim or misfire–related
DTC, additional requirements must be met. In addition to
the requirements stated in the previous paragraph, these
requirements are as follows:

The diagnostic tests that are passed must occur with
375 RPM of the RPM data stored at the time the last
test failed.

Plus or minus ten (10) percent of the engine load that
was stored at the time the last test failed.

Similar engine temperature conditions (warmed up or
warming up) as those stored at the time the last test
failed.

Meeting these requirements ensures that the fault which
turned on the MIL has been corrected.
The MIL (”Check Engine” lamp) is on the instrument panel
and has the following functions:

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.

As a bulb and system check, the MIL will come ON
with the key ON and the engine not running. When the
engine is started, the MIL will turn OFF.

6E1–35

RODEO Y22SE 2.2L ENGINE DRIVEABILITY AND EMISSION

When the MIL remains ON while the engine is
running, or when a malfunction is suspected due to a
driveability or emissions problem, a Powertrain
On–Board Diagnostic (OBD) System Check must be
performed. The procedures for these checks are
given in On–Board Diagnostic (OBD II) System
Check. These checks will expose faults which may
not be detected if other diagnostics are performed
first.

DTC Types

Each 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 (2) consecutive trips before the DTC is set. The
following are the four (4) types of DTCs and the
characteristics of those codes:

Type A

Emissions related

Requests illumination of the MIL of the first trip with a
fail

Stores a History DTC on the first trip with a fail

Stores a Freeze Frame (if empty)

Stores a Fail Record

Updates the Fail Record each time the diagnostic
test fails

Type B

Emissions related

”Armed” after one (1) trip with a fail

”Disarmed” after one (1) trip with a pass

Requests illumination of the MIL on the

second

consecutive trip with a fail

Stores a History DTC on the second consecutive trip
with a fail (The DTC will be armed after the first fail)

Stores a Freeze Frame on the second consecutive
trip with a fail (if empty)

Stores a Fail Record when the first test fails (not
dependent on

consecutive trip fails)

Updates the Fail Record each time the diagnostic
test fails

(Some special conditions apply to misfire and fuel trim
DTCs)

Type C (if the vehicle is so equipped)

Non–Emissions related

Requests illumination of the Service Lamp or the
service message on the Drive Information Center
(DIC) on the

first trip with a fail

Stores a History DTC on the

first trip with a fail

Does not store a Freeze Frame

Stores Fail Record when test fails

Updates the Fail Record each time the diagnostic
test fails

Type D. (

Type D non–emissions related are not

utilized on certain vehicle applications).

Non–Emissions related

Does not request illumination of any lamp

Stores a History DTC on the

first trip with a fail

Does not store a Freeze Frame

Stores Fail Record when test fails

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
potentially damaging levels of misfire. If a misfire
condition exists 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

diagnostics. Each time a fuel trim or misfire malfunction is
detected, engine load, engine speed, and engine coolant
temperature are recorded.
When the ignition is turned OFF, the last reported set of
conditions 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 normal

Type B diagnostic, and does not use

the stored conditions. However, if a malfunction occurs on
two non–consecutive trips, the stored conditions are
compared with the current conditions. The MIL will then
illuminate under the following conditions:

When the engine load conditions are within 10% of
the previous test that failed.

Engine speed is within 375 rpm, of the previous test
that failed.

Engine coolant temperature is in the same range as
the previous test that failed.

Storing and Erasing Freeze Frame Data and Failure
Records
Government regulations require that engine operating
conditions be captured whenever the MIL is illuminated.
The data captured is called Freeze Frame data. The
Freeze Frame data is very similar to a single record of
operating conditions. Whenever the MIL is illuminated,
the corresponding record of operating conditions is
recorded to the Freeze Frame buffer.
Freeze Frame data can only be overwritten with data
associated with a misfire or fuel trim malfunction. Data
from these faults take precedence over data associated
with any other fault. The Freeze Frame data will not be
erased unless the associated history DTC is cleared.
Each time a diagnostic test reports a failure, the current
engine operating conditions are recorded in the

Failure

Records buffer. A subsequent failure will update the
recorded operating conditions. The following operating
conditions for the diagnostic test which failed

typically

include the following parameters:

Air Fuel Ratio

Air Flow Rate

Content .. 1237 1238 1239 1240 ..