2004 ISUZU TF SERIES fuel

6E-60 3.5L ENGINE DRIVEABILITY AND EMISSIONS



TS2394
A broken or cracked lower insulator tip (around the
center electrode) may result from “heat shock" (spark
plug suddenly operating too hot).



TS23993

"Heat shock" breakage in the lower insulator tip
generally occurs during several engine operating
conditions (high speeds or heavy loading) and may
be caused by over-advanced timing or low grade
fuels. Heat shock refers to a rapid increase in the
tip temperature that causes the insulator material
to crack.
If there is any doubt about the serviceability of a spark
plug, replace it. Spark plugs with cracked or broken
insulators should always be replaced.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-61
GENERAL DESCRIPTION FOR
EVAPORATIVE EMISSION SYSTEM




3 1 2
(1) Purge Solenoid Valve
(2) From Canistor to Purge Solenoid
(3) From Purge Solenoid to Intake








1
2
(1) Canistor
(2) Air Separator


The basic evaporative emission control system used on
the charcoal canister storage method. The method
transfers fuel vapor from the fuel tank to an activated
carbon (charcoal) storage devise to hold the vapors
when the vehicle is not operating.
The canister is located on the rear axle housing by the
frame cross-member.
When the engine is running, the fuel vapor is purged
from the carbon element by intake air flow and
consumed in the normal combustion process.

EVAP Control System
The evaporate emission canister purge is controlled by
a duty solenoid valve that allows manifold to purge the
canister when following operating conditions are met.
Purge solenoid valve operating condition at idle
condition:

Engine speed is below 1000rpm.

Vehicle speed is below 3km/h.

Engine coolant temperature is more than 80C.

Intake air temperature is more than 10C.

In closed loop operation.
All above conditions are met for 4 seconds.

Purge solenoid valve operating condition at other than
idle condition:

Engine speed is below 6375rpm.

Vehicle speed is more than 14km/h.

Engine coolant temperature is more than 60C.
All above conditions are met for 4 seconds.


Results of Incorrect Operation
Poor idle, stalling and poor driveability can be caused
by:

Inoperative purge solenoid.

Damaged canister.

Hoses split, cracked and/or not connected to the
proper tubes.
Evidence of fuel loss or fuel vapor odor can be caused
by:

Liquid fuel leaking from fuel lines, or fuel pump.

Cracked or damaged canister.

Disconnected, misrouted, kinked, deteriorated o
r
damaged vapor hoses, or control hoses.
If the solenoid is always open, the canister can purge to
the intake manifold at all times. This can allow extra fuel
at idle or during warm-up, which can cause rough o
r
unstable idle, or too rich operation.
If the solenoid is always closed, the canister can
become over-loaded, resulting in fuel odor.

6E-62 3.5L ENGINE DRIVEABILITY AND EMISSIONS
GENERAL DESCRIPTION FOR EXHAUST
GAS RECIRCULATION (EGR) SYSTEM
Linear EGR Valve









060R200237
Legend
(1) ECM
(2) Linear EGR Valve
(3) Throttle
(4) Exhaust Manifold


The exhaust gas re-circulation (EGR) system is used to
reduce emission levels of oxides of nitrogen (NOx).
NOx emission levels are caused by a high combustion
levels by decreasing the combustion temperature.
The EGR valve feeds small amount of exhaust gas
back into the combustion chamber. The fuel/air mixture
will be diluted and combustion temperatures reduced.
Linear EGR valve Operation and Results o
f
Incorrect Operation
The linear EGR valve is designed to accurately supply
EGR to the engine independent of intake manifold
vacuum. The valve controls EGR flow from the exhaus
t
to the intake manifold through an orifice with a ECM
controlled pintle. During operation, the ECM controls
pintle position by monitoring the pintle position feedback
signal.

The linear EGR valve is activated under the following
conditions:

No DTC relating to the EGR.

Engine speed is between 1200 and 4375rpm.

Engine coolant temperature is between 20 and
100
.

Throttle position sensor output voltage is belo
w
3V.

Too mach EGR flow at idle, cruise or cold operation
may cause any of the following conditions to occur:

Engine stalls after a cold start.

Engine stalls at idle after deceleration.

Vehicle surges during cruise.

Rough idle.

Too little or no EGR flow may allow combustion
temperatures to get too high. This could cause:

Spark knock (detonation).

Emission test failure.

Poor fuel economy.

6E-70 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Fuel Quality
Fuel quality is not a new issue for the automotive
industry, but its potential for turning on the MIL (“Check
Engine" lamp) with OBD systems is new.
Fuel additives such as “dry gas" and “octane
enhancers" may affect the performance of the fuel. The
Reed Vapor Pressure of the fuel can also create
problems in the fuel system, especially during the spring
and fall months when severe ambient temperature
swings occur. A high Reed Vapor Pressure could sho
w
up as a Fuel Trim DTC due to excessive canister
loading. High vapor pressures generated in the fuel
tank can also affect the Evaporative Emission
diagnostic as well.
Using fuel with the wrong octane rating for your vehicle
may cause driveability problems. Many of the majo
r
fuel companies advertise that using “premium" gasoline
will improve the performance of your vehicle. Mos
t
premium fuels use alcohol to increase the octane rating
of the fuel. Although alcohol-enhanced fuels may raise
the octane rating, the fuel's ability to turn into vapor in
cold temperatures deteriorates. This may affect the
starting ability and cold driveability of the engine.
Low fuel levels can lead to fuel starvation, lean engine
operation, and eventually engine misfire.
Non-OEM Parts
All of the OBD diagnostics have been calibrated to run
with OEM parts.
Aftermarket electronics, such as cellular phones,
stereos, and anti-theft devices, may radiate EMI into the
control system if they are improperly installed. This may
cause a false sensor reading and turn on the MIL
(“Check Engine" lamp).
Environment
Temporary environmental conditions, such as localized
flooding, will have an effect on the vehicle ignition
system. If the ignition system is rain-soaked, it can
temporarily cause engine misfire and turn on the MIL
(“Check Engine" lamp).
Vehicle Marshaling
The transportation of new vehicles from the assembly
plant to the dealership can involve as many as 60 key
cycles within 5Km miles of driving. This type o
f
operation contributes to the fuel fouling of the spark
plugs and will turn on the MIL (“Check Engine" lamp).

Poor Vehicle Maintenance
The sensitivity of OBD diagnostics will cause the MIL
(“Check Engine" lamp) to turn on if the vehicle is no
t
maintained properly. Restricted air filters, fuel filters,
and crankcase deposits due to lack of oil changes o
r
improper oil viscosity can trigger actual vehicle faults
that were not previously monitored prior to OBD. Poo
r
vehicle maintenance can not be classified as a
“non-vehicle fault", but with the sensitivity of OBD
diagnostics, vehicle maintenance schedules must be
more closely followed.
Severe Vibration
The Misfire diagnostic measures small changes in the
rotational speed of the crankshaft. Severe driveline
vibrations in the vehicle, such as caused by an
excessive amount of mud on the wheels, can have the
same effect on crankshaft speed as misfire.
Related System Faults
Many of the OBD system diagnostics will not run if the
ECM detects a fault on a related system or component.
One example would be that if the ECM detected a
Misfire fault, the diagnostics on the catalytic converte
r
would be suspended until Misfire fault was repaired. If
the Misfire fault was severe enough, the catalytic
converter could be damaged due to overheating and
would never set a Catalyst DTC until the Misfire faul
t
was repaired and the Catalyst diagnostic was allowed to
run to completion. If this happens, the customer may
have to make two trips to the dealership in order to
repair the vehicle.
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 punches, cuts,
disconnects, and correct routing.

Inspect hoses that are difficult to see behind othe
r
components.

Inspect all wires in the engine compartment fo
r
proper connections, burned or chafed spots, pinched
wires, contact with sharp edges or contact with ho
t
exhaust manifolds or pipes.

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-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.

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.