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Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 825

6E–29

3.2L ENGINE DRIVEABILITY AND EMISSIONS

060RW032

Menu

The following table shows, which functions are used
the available equipment versions.

F0: Diagnostic Trouble Codes

F0: Read DTC Info Ordered By Priority

F1: Clear DTC Information

F2: DTC Information

F0: History

F1: MIL SVS or Message Requested

F2: Last Test Failed

F3: Test Failed Since Code Cleared

F4: Not Ran Since Code Cleared

F5: Failed This Ignition

F3: Freeze Frame Data/Failure Record

F1: Data Display

F0: Engine Data

F2: Snapshot

F3: Miscellaneous Tests

F0: Lamps

F0: MIL

F1: Relays

F1: A/C Relay

F2: Fuel Pump Relay

F2: EVAP

F0: Canister Purge Solenoid

F3: IAC System

F0: RPM Control

F1: IAC Control

F4: Fuel System

F1: Fuel Trim Reset

6E–30

3.2L ENGINE DRIVEABILITY AND EMISSIONS

DTC Modes

On OBD passenger cars there are three options available
in the Tech 2 DTC mode to display the enhanced
information available. A description of the new modes,
DTC Info and Specific DTC, follows. After selecting DTC,
the following menu appears:

DTC Info

Clear Info

Read DTC Info Ordered By Priority

Freeze Frame

The following is a brief description of each of the sub
menus in DTC Info. The order in which they appear here is
alphabetical and not necessarily the way they will appear
on the Tech 2.

DTC Information Mode

Use the DTC info mode to search for a specific type of
stored DTC information. There are six choices. The
service manual may instruct the technician to test for
DTCs in a certain manner. Always follow published
service procedures.
To get a complete description of any status, press the
“Enter” key before pressing the desired F-key. For
example, pressing “Enter” then an F-key will display a
definition of the abbreviated Tech 2 status.

Fail This Ignition
This selection will display all DTCs that have failed during
the present ignition cycle.

History
This selection will display only DTCs that are stored in the
PCM’s history memory. It will not display Type B DTCs
that have not requested the MIL (“Check Engine” lamp). It
will display all type A and B DTCs that have requested the
MIL and have failed within the last 40 warm-up cycles. In
addition, it will display all type C and type D DTCs that
have failed within the last 40 warm-up cycles.

Last Test Failed
This selection will display only DTCs that have failed the
last time the test ran. The last test may have run during a
previous ignition cycle if a type A or type B DTC is
displayed. For type C and type D DTCs, the last failure
must have occurred during the current ignition cycle to
appear as Last Test Fail.

MIL SVC or Message Requested
This selection will display only DTCs that are requesting
the MIL. Type C and type D DTCs cannot be displayed
using this option. This selection will report type B DTCs
only after the MIL has been requested.

Not Run Since Code Cleared
This option will display up to 33 DTCs that have not run
since the DTCs were last cleared. Since any displayed
DTCs have not run, their condition (passing or failing) is
unknown.

Test Failed Since Code Cleared
This selection will display all active and history DTCs that
have reported a test failure since the last time DTCs were
cleared. DTCs that last failed more than 40 warm-up
cycles before this option is selected will not be displayed.

Primary System-Based Diagnostics

There are primary system-based diagnostics which
evaluate system operation and its effect on vehicle
emissions. The primary system-based diagnostics are
listed below with a brief description of the diagnostic
function:

Oxygen Sensor Diagnosis
The fuel control heated oxygen sensors are diagnosed for
the following conditions:

Inactive signal (output steady at bias voltage – approx.
450 mV)

Signal fixed high

Signal fixed low

If the oxygen sensor pigtail wiring, connector or terminal
are damaged, the entire oxygen sensor assembly must
be replaced. DO NOT attempt to repair the wiring,
connector or terminals. In order for the sensor to function
properly, it must have clean reference air provided to it.
This clean air reference is obtained by way of the oxygen
sensor wire(s). Any attempt to repair the wires, connector
or terminals could result in the obstruction of the
reference air and degrade oxygen sensor performance.
Refer to

On-Vehicle Service Heated Oxygen Sensors.

Fuel Control Heated Oxygen Sensors

The main function of the fuel control heated oxygen
sensors is to provide the control module with exhaust
stream oxygen content information to allow proper fueling
and maintain emissions within mandated levels. After it
reaches operating temperature, the sensor will generate
a voltage, inversely proportional to the amount of oxygen
present in the exhaust gases. The control module uses
the signal voltage from the fuel control heated oxygen
sensors while in closed loop to adjust fuel injector pulse
width. While in closed loop, the ECM can adjust fuel
delivery to maintain an air/fuel ratio which allows the best
combination of emission control and driveability. The fuel
control heated oxygen sensors are also used to
determine catalyst efficiency.

HO2S Heater

Heated oxygen sensors are used to minimize the amount
of time required for closed loop fuel control to begin
operation and to allow accurate catalyst monitoring. The
oxygen sensor heater greatly decreases the amount of
time required for fuel control sensors to become active.
Oxygen sensor heaters are required by catalyst monitor
and sensors to maintain a sufficiently high temperature
which allows accurate exhaust oxygen content readings
further away from the engine.

6E–31

3.2L ENGINE DRIVEABILITY AND EMISSIONS

Fuel Trim System Monitor Diagnostic

Operation

Fuel Trim System Monitor Diagnostic
Operation

This system monitors the averages of short-term and
long-term fuel trim values. If these fuel trim values stay at
their limits for a calibrated period of time, a malfunction is
indicated. The fuel trim diagnostic compares the
averages of short-term fuel trim values and long-term fuel
trim values to rich and lean thresholds. If either value is
within the thresholds, a pass is recorded. If both values
are outside their thresholds, a rich or lean DTC will be
recorded.
The fuel trim system diagnostic also conducts an intrusive
test. This test determines if a rich condition is being
caused by excessive fuel vapor from the EVAP canister.
In order to meet OBD requirements, the control module
uses weighted fuel trim cells to determine the need to set
a fuel trim DTC. A fuel trim DTC can only be set if fuel trim
counts in the weighted fuel trim cells exceed
specifications. This means that the vehicle could have a
fuel trim problem which is causing a problem under
certain conditions (i.e., engine idle high due to a small
vacuum leak or rough idle due to a large vacuum leak)
while it operates fine at other times. No fuel trim DTC
would set (although an engine idle speed DTC or HO2S
DTC may set). Use a Tech 2 to observe fuel trim counts
while the problem is occurring.
A fuel trim DTC may be triggered by a number of vehicle
faults. Make use of all information available (other DTCs
stored, rich or lean condition, etc.) when diagnosing a fuel
trim fault.

Fuel Trim Cell Diagnostic Weights

No fuel trim DTC will set regardless of the fuel trim counts
in cell 0 unless the fuel trim counts in the weighted cells
are also outside specifications. This means that the
vehicle could have a fuel trim problem which is causing a
problem under certain conditions (i.e. engine idle high due
to a small vacuum leak or rough due to a large vacuum
leak) while it operates fine at other times. No fuel trim
DTC would set (although an engine idle speed DTC or
HO2S DTC may set). Use a Tech 2 to observe fuel trim
counts while the problem is occurring.

6E–32

3.2L ENGINE DRIVEABILITY AND EMISSIONS

On-Board Diagnostic (OBD) System Check

060RW045

Circuit Description

The on-board diagnostic system check is the starting
point for any driveability complaint diagnosis. Before
using this procedure, perform a careful visual/physical
check of the ECM and engine grounds for cleanliness and
tightness.
The on-board diagnostic system check is an organized
approach to identifying a problem created by an
electronic engine control system malfunction.

Diagnostic Aids

An intermittent may be caused by a poor connection,
rubbed-through wire insulation or a wire broken inside the
insulation. Check for poor connections or a damaged
harness. Inspect the ECM harness and connector for
improper mating, broken locks, improperly formed or
damaged terminals, poor terminal-to-wire connection,
and damaged harness.

Test Description

Number(s) below refer to the step number(s) on the
Diagnostic Chart:
1. The MIL (“Check Engine” lamp) should be “ON”

steady with the ignition “ON”/engine “OFF.” If not,
the “No Malfunction Indicator Lamp (MIL)” chart
should be used to isolate the malfunction.

2. Checks the Class 2 data circuit and ensures that the

ECM is able to transmit serial data.

3. This test ensures that the ECM is capable of

controlling the MIL (“Check Engine” lamp) and the
MIL (“Check Engine” lamp) driver circuit is not
shorted to ground.

4. If the engine will not start, the

Cranks But Will Not

Run chart should be used to diagnose the condition.

7. A Tech 2 parameter which is not within the typical

range may help to isolate the area which is causing
the problem.

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