Opel Frontera UBS. Manual - part 474

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4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

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:

EGR VSV

EGR EVRV

Electronic Transmission controls

Injector

Intake throttle

Glow plug

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

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
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 OBD 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:

EGR

engine speed

vehicle speed

ECT

MAP

VSV

IAT

ITP

FT (Fuel Temp)

RP (Rail Pressure)

OT (Oil Temp)

EGR EVRV

Idle SW

Brake SW

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

Current status information on each diagnostic

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 not multiple faults
present.
There is a continuous self-diagnosis on certain control
functions. This diagnostic capability is complemented 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.
Basically, the MIL is turned on when the ECM detects a
DTC that will impact the vehicle emissions.

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) System Check.
These checks will expose faults which may not be
detected if other diagnostics are performed first.

DTC Types

Characteristic of Code

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4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Non-Emissions related

Dose not request illumination of any lamp

Stores a History DTC on the

first trip with a fail

Stores Fail Record when test fails

Updates the Fail Record each time the diagnostic test
fails

Storing and Erasing Freeze Frame Data and Failure
Records
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.
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:

Engine Speed

Engine Load

Engine Coolant Temperature

Vehicle Speed

Intake Throttle Position

MAP

Injector Base Pulse Width

Loop Status

Data Link Connector (DLC)
The provision for communication with the contorl module
is the Data Link Connector (DLC). It is located at behind
the lower front instrument panel. The DLC is used to
connect to a Tech 2. Some common uses of the Tech 2
are listed below:

Identifying stored Diagnostic Trouble Codes (DTCs).

Clearing DTCs.

Performing out put control tests.

Reading serial data.

060RW046

Verifying Vehicle Repair

Verification of vehicle repair will be more comprehensive
for vehicles with OBD system diagnostic. Following a
repair, the technician should perform the following steps:

1. Review and record the Fail Records and/or Freeze

Frame data for the DTC which has been diagnosed.

2. Clear DTC(s).
3. Operate the vehicle within conditions noted in the Fail

Records and/or Freeze Frame data.

4. Monitor the DTC status information for the specific

DTC which has been diagnosed until the diagnostic
test associated with that DTC runs.

Following these steps are very important in verifying
repairs on OBD systems. Failure to follow these steps
could result in unnecessary repairs.

Reading Flash Diagnostic Trouble Codes

The provision for communicating with the Engine Control
Module (ECM) is the Data Link Connector (DLC). The
DLC is located in the front console box. It is used in the
assembly plant to receive information in checking that the
engine is operating properly before it leaves the plant.
The diagnostic trouble code(s) (DTCs) stored in the
ECM’s memory can be read either through a hand-held
diagnostic scanner plugged into the DLC or by counting
the number of flashes of the “Check Engine” Malfunction
Indicator Lamp (MIL) when the diagnostic test terminal of
the DLC is grounded. The DLC terminal “6” (diagnostic
request) is pulled “Low” (grounded) by jumpering to DLC
terminal “4”, which is a ground wire.
This will signal the ECM that you want to “flash” DTC(s), if
any are present. Once terminals “4” and “6” have been
connected, the ignition switch must be moved to the “ON”
position, with the engine not running.
The “Check Engine”MIL will indicate a DTC three times if
a DTC is present. If more than one DTC has been stored

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4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

in the ECM’s memory, the DTC(s) will be output from the
lowest to the highest, with each DTC being displayed
three times.
The DTC display will continue as long as the DLC is
shorted.

Reading Diagnostic Trouble Codes Using
a TECH 2

The procedure for reading diagnostic trouble code(s) is to
used a diagnostic Tech 2. When reading DTC(s), follow
instructions supplied by Tech 2 manufacturer.
For the 1998 model year, Isuzu dealer service
departments will continue to use Tech 2.

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
and Failure Record data which may help diagnose an
intermittent fault will also be erased from memory.
If the fault that caused the DTC to be stored into memory
has been corrected, the Diagnostic Executive will begin to
count the “warm-up” cycles with no further faults
detected, the DTC will automatically be cleared from the
ECM memory.

To clear Diagnostic Trouble Codes (DTCs), use the Tech
2 “clear DTCs” or “clear information” function. When
clearing DTCs follow instructions supplied by the Tech 2
manufacturer.
When a Tech 2 is not available, DTCs can also be cleared
by disconnecting

one of the following sources for at least

thirty (30) seconds.

NOTE: To prevent system damage, the ignition key must
be “OFF” when disconnecting or reconnecting battery
power.

The power source to the control module. Examples:
fuse, pigtail at battery ECM connectors etc.

The negative battery cable. (Disconnecting the
negative battery cable will result in the loss of other
on-board memory data, such as preset radio tuning).

060RW169

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4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

Tech 2 Scan Tool

From 98 MY, Isuzu dealer service departments are
recommended to use Tech 2. Please refer to Tech 2 user
guide.

901RW257

Legend

(1) PCMCIA Card
(2) SAE 16/19 Adaptor

(3) DLC Cable
(4) Tech–2

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