2004 ISUZU TF SERIES display

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-71
Basic Knowledge of Tools Required
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
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 fo
r
vehicle parameters. It will not be necessary to perform
any conversions from coded values to actual values.
On-Board Diagnostic (OBD)
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 curren
t
ignition cycle.

The fault identified by the diagnostic test is no
t
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 o
f
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
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 sensor that indicates
high throttle position at low engine loads. Inpu
t
components may include, but are not limited to the
following sensors:

Vehicle Speed Sensor (VSS)

Inlet Air Temperature (IAT) Sensor

Crankshaft Position (CKP) Sensor

Throttle Position Sensor (TPS)

Engine Coolant Temperature (ECT) Sensor

Camshaft Position (CMP) Sensor

Mass Air Flow (MAF) 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.
Output Components:
Output components are diagnosed for proper response
to control module commands. Components where
functional monitoring is not feasible will be monitored fo
r
circuit continuity and out-of-range values if applicable.
Output components to be monitored include, but are no
t
limited to, the following circuit:

Idle Air Control (IAC) Valve

Control module controlled EVAP Canister Purge
Valve

Electronic Transmission controls

A/C relays

VSS output

MIL control
Refer to ECM and Sensors in General Descriptions.

6E-72 3.5L ENGINE DRIVEABILITY AND EMISSIONS
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) andrise at
least 22

C (40
F) over the course of a trip.
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
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
t
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 MIL (“Check
Engine" lamp) is illuminated.

Check Engine Lamp (MIL)
The Check Engine 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.
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 emissionsrelated faults.
Extinguishing the MIL
When the MIL is on, the Diagnostic Executive will turn
off the MIL after three consecutive trips that a “tes
t
passed" has been reported for the diagnostic test tha
t
originally caused the MIL to illuminate.
Although the MIL has been turned off, the DTC will
remain in the ECM 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 las
t
test failed.

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

Similar engine temperature conditions (warmed up o
r
warming up ) as those stored at the time the last tes
t
failed.
Meeting these requirements ensures that the fault which
turned on the MIL has been corrected.
The MIL (“Check Engine" lamp) is on the instrumen
t
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."

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.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-73
Intermittent Check Engine Lamp
In the case of an “intermittent" fault, the MIL (“Check
Engine" lamp) may illuminate and then (after three trips)
go “OFF". However, the corresponding diagnostic
trouble code will be stored in the memory. When
unexpected diagnostic trouble codes appear, check fo
r
an intermittent malfunction.
A diagnostic trouble code may reset. Consult the
“Diagnostic Aids" associated with the diagnostic trouble
code. A physical inspection of the applicable sub–
system most often will resolve the problem.
Data Link Connector (DLC)
The provision for communication with the control
module is the Data Link Connector (DLC). The DLC is
used to connect to a Tech 2. Some common uses o
f
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
(Freeze Frame data will only be stored for an A or B
type diagnostic and only if the MIL has been
requested).
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 verifyin
g
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 Connecto
r
(DLC). The DLC is located behind the lower front
instrument panel. 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 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. At this
point, the “Check Engine" MIL should flash DTC12
three times consecutively.
This would be the following flash, sequence: "flash,
pause, flash?flash, long pause, flash, pause,
flash?flash, long pause, flash, pause, flash?flash". DTC
12 indicates that the ECM's diagnostic system is
operating. If DTC 12 is not indicated, a problem is
present within the diagnostic system itself, and should
be addressed by consulting the appropriate diagnostic
chart in DRIVEABILITY AND EMISSIONS.
Following the output of DTC 12, the “Check Engine" MIL
will indicate a DTC three times if a DTC is present, or i
t
will simply continue to output DTC12. If more than one
DTC three has been stored in the ECM's memory, the
DTC(s) will be output from the lowest to the highest,
with each DTC being displayed three times.
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.

6E-74 3.5L ENGINE DRIVEABILITY AND EMISSIONS








0.4 Sec 0.4 Sec
.

ON

OFF




3.2 Sec.

1.2 Sec.



3.2 Sec.


0.4 Sec 0.4 Sec
.
ON

OFF


3.2 Sec.

1.2 Sec.


3.2 Sec.



Self-diagnosis Start

Normal Code (12)
Trouble Code (32)


121212141414323232

In case DTC 14 & 32 are stored

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 furthe
r
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.
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 othe
r
on-board memory data, such as preset radio tuning).
On-Board Diagnosis (Self-Diagnosis)
1. The Engine Control Module (ECM) conducts a
self-test of most of the wiring and components in
the system each time the key is turned to ON, and
can detect faults in the system while the key is ON.
If a fault is detected, the ECM will store a trouble
code in memory and flash the CHECK ENGINE
indicator to alert the driver.
2. The Diagnostic Trouble Codes (DTC) can be
displayed by shorting together terminals and the
Data Link Connector (DLC) located belo
w
Instrument Panel of drivers side.
The CHECK ENGINE indicator will flash DTC 12
three times, followed by any DTC.If several DTC are
stored, each DTC will be displayed three times. The
DTC will be displayed in numerical order. The DTC
display will continue as long as the DLC is shorted.
Some DTC can cause other DTC to be stored, It is
important to diagnose and repair the lowes
t
numbered DTC first before going on to the highe
r
numbered DTC.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-75
TECH 2 CONNECTION



Tech 2 scan tool is used to electrically diagnose the
automatic transmission system and to check the
system. The Tech 2 enhances the diagnosis efficiency
though all the troubleshooting can be done without the
Te c h 2 .
1. Configuration of Tech 2

Tech 2 scan tool kit (No. 7000086), Tech 2
scan tool (No. 7000057) and DLC cable (No.
3000095).

SAE 16/19 adapter (No. 3000098) (3), RS232
loop back connector (No. 3000112) (2) and
PCMCIA card (No. 3000117) (1).
2. Tech 2 Connection

Check the key switch is turn OFF.

Insert the PCMCIA card (1) into the Tech 2 (5).

Connect the SAE 16/19 adapter (3) to the DLC





Turn the key switch of the vehicle ON and press
the “PWR” key of the Tech 2.

Check the display of the Tech 2.
NOTE: Be sure to check that the power is not
supplied to the Tech 2 when attaching or removing
the PCMCIA card.
Diagnosis with TECH 2
If No Codes are Set

Refer to F1: Data Display and identify the electrical
faults that are not indicated by trouble code.

Refer to "SYMPTOM DIAGNOSIS".

If Codes are Set
1. Record all trouble codes displayed by Tech 2 and
check id the codes are intermittent.
2. Clear the codes.
3. Drive the vehicle for a test to reproduce the faulty
status.
4. Check trouble codes again using the Tech 2.
5. If no codes is displayed by test driving, the fault is
intermittent. In this case, refer to "DIAGNOSIS
AIDS".
6. If a code is present, refer to DTC Chartfo
r
diagnosis.
7. Check trouble codes again using the Tech 2.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-77


F0: Diagnostic Trouble Code
F0: Read DTC Infor 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 Run Since Code Cleared
F5: Failed This Ignition
F3: Freeze Frame/Failure Record
F1: Data Display
F0: Engine Data
F1: O2 Sensor Data
F2: Snapshot
F3: Miscellaneous Test
F0: Lamps
F0: Malfunction Indicator Lamps
F1: Relays
F0: Fuel Pump Relay
F1: A/C Clutch Relay
F2: EVAP
F0: Purge Solenoid
F3: IAC System
F0: RPM Control
F1: IAC Control
F4: Fuel System
F0: Fuel Trim Reset

F4: System Information
F0: MIL/System Status

F0: Diagnostic Trouble Code
The purpose of the "Diagnostic Trouble Codes" mode is
to display stored trouble code in the
ECM.
When "Clear DTC Information" is selected, a "Clea
r
DTC Information", warning screen appears.
This screen informs you that by cleaning DTC's "all
stored DTC information in the ECM will be erased".
After clearing codes, confirm system operation by test
driving the vehicle.
Use the "DTC Information" mode to search for a
specific type of stored DTC information.
History
This selection will display only DTCs that are stored in
the ECM'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 tha
t
requested the MIL and have failed within the last 40
warm-up cycles. In addition, it will display all type C and
D DTCs that have failed within the last 40 warm-up
cycles.

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

Last Test Failed
This selection will display only DTCs that have failed the
last time the test run. The last test may have run during
a previous ignition cycle of 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.

Test Failed Since Code Cleared
The 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 that 40
warm-up cycles before this option is selected will not be
displayed.

Not Run Since Code Cleared
This selection will display up to 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.

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

Freeze Frame/Failure Record
This selection will display stored various vehicle
information at the moment an emission related faul
t
when the MIL ("Check Engine Lamp") is commanded
on.
The Freeze Frame data will not be erased unless the
associated history DTC is cleared.

6E-78 3.5L ENGINE DRIVEABILITY AND EMISSIONS
F1: Data Display
The purpose of the "Data Display" mode is to
continuously monitor data parameters.
The current actual values of all important sensors and
signals in the system are display through F1 mode.
See the "Typical Scan Data" section.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-79
TYPICAL SCAN DATA & DEFINITIONS (ENGINE DATA)
Use the typical values table only after the On-Board Diagnostic System check has been completed, no DTC(s) were noted, and you have determined that the On-Board
Diagnostic are functioning properly.
Tech2 values from a properly running engine may be used for comparison with the engine you are diagnosing.
Condition : Vehicle stopping, engine running, air conditioning off & after warm-up (Coolant temperature approximately 80
C)

Tech 2
Parameter
Units Idle 2000rpm Definitions
1 Ignition Voltage V 10.0  14.5 10.0  14.5 This displays the system voltage measured by the ECM at ignition feed.
2 Engine Speed rpm 710  860 1950  2050 The actual engine speed is measured by ECM from the CKP sensor 58X signal.
3 Desired Idle
Speed rpm 750  770 750  770 The desired engine idle speed that the ECM commanding.
The ECM compensates for various engine loads.
4 Engine Coolant
Temperature
C or
F 80  90 (

) 80  90 (

) The ECT is measured by ECM from ECT sensor output voltage.
When the engine is normally warm upped, this data displays approximately 80 °C or
more.
5 Start Up ECT
(Engine Coolant
Temperature)
C or
F Depends on ECT
at start-up
Depends on ECT
at start-up
Start-up ECT is measured by ECM from ECT sensor output voltage when engine is
started.
6 Intake Air
Temperature

C or
F Depends on
ambient temp.
Depends on
ambient temp.
The IAT is measured by ECM from IAT sensor output voltage.
This data is changing by intake air temperature.
7 Throttle Position % 0 4  6 Throttle position operating angle is measured by the ECM from throttle position
output voltage.
This should display 0% at idle and 99  100% at full throttle.
8 Throttle Position
Sensor V 0.4  0.7 0.6  0.8 The TPS output voltage is displayed.
This data is changing by accelerator operating angle.
9 Mass Air Flow g/s 5.0  8.0 13.0  16.0 This displays intake air amount.
The mass air flow is measured by ECM from the MAF sensor output voltage.
10 Air Fuel Ratio 14.7:1 14.7:1 This displays the ECM commanded value.
In closed loop, this should normally be displayed around 14.2:1  14.7:1.
11 Idle Air Control Steps 10  20 20  30 This displays the ECM commanded position of the idle air control valve pintle.
A larger number means that more air is being commanded through the idle air
passage.
12 EGR Valve V 0.00 0.00  0.10 The EGR position sensor output voltage is displayed.
This data is changing by EGR valve solenoid operating position.
13 Desired EGR
Opening V 0.00 0.05  1.10 The ECM commanded EGR position sensor voltage is displayed.
According to the current position, ECM changes EGR valve solenoid operating
position to meet the desired position.
14 EGR Valve On
Duty % 0 32 – 38 This displays the duty signal from the ECM to control the EGR valve.
15 Engine Load % 2  7 8  15 This displays is calculated by the ECM form engine speed and MAF sensor reading.
Engine load should increase with an increase in engine speed or air flow amount.
16 B1 Fuel System
Status Open Loop/ Close
Loop Close Loop Close Loop
17 B2 Fuel System
Status Open Loop/ Close
Loop Close Loop Close Loop
When the engine is first started the system is in "Open Loop" operation.
In "Open Loop", the ECM ignores the signal from the oxygen sensors.
When various conditions (ECT, time from start, engine speed & oxygen sensor
output) are met, the system enters "Closed Loop" operation.
In "Closed Loop", the ECM calculates the air fuel ratio based on the signal from the
oxygen sensors.
18 Fuel Trim
Learned (Bank 1) Yes/No Yes Yes
19 Fuel Trim
Learned (Bank 2) Yes/No Yes Yes
When conditions are appropriate for enabling long term fuel trim corrections, fuel trim
learn will display "Yes".
This indicates that the long term fuel trim is responding to the short term fuel trim.
If the fuel trim lean displays "No", then long term fuel trim will not respond to changes
in short term fuel trim.
20 Injection Pulse
Bank 1 ms 2.0  4.0 2.0  4.0
21 Injection Pulse
Bank 2 ms 2.0  4.0 2.0  4.0
This displays the amount of time the ECM is commanding each injector On during
each engine cycle.
A longer injector pulse width will cause more fuel to be delivered. Injector pulse width
should increase with increased engine load.
22 Spark Advance °CA 10  15 35  42 This displays the amount of spark advance being commanded by the ECM.