2004 ISUZU TF SERIES fuse

6E-64 3.5L ENGINE DRIVEABILITY AND EMISSIONS
Diagnostic Thought Process
As you follow a diagnostic plan, every box on the
Strategy Based Diagnostics chart requires you to use
the diagnostic thought process. This method of thinking
optimizes your diagnosis in the following ways:

Improves your understanding and definition of the
customer complaint

Saves time by avoiding testing and/or replacing
good parts


Allows you to look at the problem from different
perspectives

Guides you to determine what level o
f
understanding about system operation is needed:
 Owner’s manual level
 Service manual level
 In-depth (engineering) level
1. Verify the Complaint
What you should do
To verify the customer complaint, you need to know the
correct (normal) operating behavior of the system and
verify that the customer complaint is a valid failure o
f
the system.
The following information will help you verify the
complaint:

WHAT the vehicle model/options are

WHAT aftermarket and dealer-installed
accessories exist

WHAT related system(s) operate properly

WHEN the problem occurs

WHERE the problem occurs

HOW the problem occurs

HOW LONG the condition has existed (and if the
system ever worked correctly)

HOW OFTEN the problem occurs

Whether the severity of the problem has
increased, decreased or stayed the same
What resources you should use
Whenever possible, you should use the following
resources to assist you in verifying the complaint:
Service manual Theory or Circuit Description
sections

Service manual “System Performance Check”

Owner manual operational description

Technician experience

Identical vehicle for comparison


Circuit testing tools

Vehicle road tests

Complaint check sheet

Contact with the customer
2. Perform Preliminary Checks
NOTE: An estimated 10 percent of successful
vehicle repairs are diagnosed with this step!
What you should do
You perform preliminary checks for several reasons:

To detect if the cause of the complaint is
VISUALLY OBVIOUS

To identify parts of the system that work correctly

To accumulate enough data to correctly and
accurately search for a ISUZU Service Bulletin.
The initial checks may vary depending on the
complexity of the system and may include the following
actions:

Operate the suspect system

Make a visual inspection of harness routing and
accessible/visible power and ground circuits

Check for blown fuses

Make a visual inspection for separated connectors

Make a visual inspection of connectors (includes
checking terminals for damage and tightness)

Check for any DTCs stored by the on-board
computers

Sense unusual noises, smells, vibrations o
r
movements

Investigate the vehicle service history (call othe
r
dealerships, if appropriate)
What resources you should use
Whenever appropriate, you should use the following
resources for assistance in performing preliminary
checks:

Tech 2 or other technical equipment for viewing
DTCs

Service manual information:
 Component locations
 Harness routing
 Wiring schematics
 Procedures for viewing DTCs

Dealership service history file

Vehicle road test

Identical vehicle or system for comparison

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-65
3. Check Bulletins and
Troubleshooting Hints
NOTE: As estimated 30 percent of successful
vehicle repairs are diagnosed with this step!
What you should do
You should have enough information gained from
preliminary checks to accurately search for a bulletin
and other related service information. Some service
manual sections provide troubleshooting hints that
match symptoms with specific complaints.
What resources you should use
You should use the following resources for assistance
in checking for bulletins and troubleshooting hints:

Printed bulletins

Access ISUZU Bulletin Web site

Videotapes

Service manual
4. Perform Service Manual
Diagnostic Checks
What you should do
The “System Checks” in most service manual sections
and in most cells of section 8A (electrical) provide you
with:


A systematic approach to narrowing down the
possible causes of a system fault

Direction to specific diagnostic procedures in the
service manual

Assistance to identify what systems work correctly
What resources you should use
Whenever possible, you should use the following
resources to perform service manual checks:

Service manual

Technical equipment (for viewing DTCs and
analyzing data)

Digital multimeter and circuit testing tools

Other tools as needed
5a and 5b. Perform Service Manual
Diagnostic Procedures
NOTE: An estimated 40 percent of successful
vehicle repairs are diagnosed with these steps!

What you should do
When directed by service manual diagnostic checks,
you must then carefully and accurately perform the
steps of diagnostic procedures to locate the fault related
to the customer complaint.
What resources you should use
Whenever appropriate, you should use the following
resources to perform service manual diagnostic
procedures:

Service manual

Technical equipment (for analyzing diagnostic
data)

Digital multimeter and circuit testing tools

Essential and special tools
5c. Technician Self Diagnoses
When there is no DTC stored and no matching
symptom for the condition identified in the service
manual, you must begin with a thorough understanding
of how the system(s) operates. Efficient use of the
service manual combined with you experience and a
good process of elimination will result in accurate
diagnosis of the condition.
What you should do
Step 1: Identify and understand the suspect
circuit(s)
Having completed steps 1 through 4 of the Strategy
Based Diagnostics chart, you should have enough
information to identify the system(s) or sub-system(s)
involved. Using the service manual, you should
determine and investigate the following circuit
characteristics:

Electrical:
 How is the circuit powered (power distribution
charts and/or fuse block details)?
 How is the circuit grounded (ground distribution
charts)?
 How is the circuit controlled or sensed (theory
of operation):
 If it is a switched circuit, is it normally open o
r
normally closed?
 Is the power switched or is the ground
switched?
 Is it a variable resistance circuit (ECT senso
r
or TPS, for example)?
 Is it a signal generating device (MAF senso
r
of VSS, for example)?

6E-66 3.5L ENGINE DRIVEABILITY AND EMISSIONS
 Does it rely on some mechanical/vacuum
device to operate?

Physical:
 Where are the circuit components (componen
t
locators and wire harness routing diagrams):

Are there areas where wires could be
chafed or pinched (brackets or frames)?

Are there areas subjected to extreme
temperatures?

Are there areas subjected to vibration or
movement (engine, transmission or
suspension)?

Are there areas exposed to moisture, road
salt or other corrosives (battery acid, oil o
r
other fluids)?

Are there common mounting areas with
other systems/components?
 Have previous repairs been performed to
wiring, connectors, components or mounting
areas (causing pinched wires between panels
and drivetrain or suspension components
without causing and immediate problem)?
 Does the vehicle have aftermarket or dealer-
installed equipment (radios, telephone, etc.)

Step 2: Isolate the problem
At this point, you should have a good idea of what could
cause the present condition, as well as could not cause
the condition. Actions to take include the following:

Divide (and separate, where possible) the system
or circuit into smaller sections

Confine the problem to a smaller area of the
vehicle (start with main harness connections while
removing panels and trim as necessary in order to
eliminate large vehicle sections from furthe
r
investigation)

For two or more circuits that do not share a
common power or ground, concentrate on areas
where harnesses are routed together o
r
connectors are shared (refer to the following hints)

Hints
Though the symptoms may vary, basic electrical failures
are generally caused by:

Loose connections:
 Open/high resistance in terminals, splices,
connectors or grounds

Incorrect connector/harness routing (usually in
new vehicles or after a repair has been made):

 Open/high resistance in terminals, splices,
connectors of grounds

Corrosion and wire damage:
 Open/high resistance in terminals, splices,
connectors of grounds

Component failure:
 Opens/short and high resistance in relays,
modules, switches or loads


Aftermarket equipment affecting normal operation
of other systems You may isolate circuits by:

Unplugging connectors or removing a fuse to
separate one part of the circuit from another part

Operating shared circuits and eliminating those
that function normally from the suspect circuit

If only one component fails to operate, begin
testing at the component

If a number of components do no operate, begin
tests at the area of commonality (such as powe
r
sources, ground circuits, switches or majo
r
connectors)
What resources you should use
Whenever appropriate, you should use the following
resources to assist in the diagnostic process:

Service manual

Technical equipment (for data analysis)

Experience

Technical Assistance

Circuit testing tools
5d. Intermittent Diagnosis
By definition, an intermittent problem is one that does
not occur continuously and will occur when certain
conditions are met. All these conditions, however, may
not be obvious or currently known. Generally,
intermittents are caused by:

Faulty electrical connections and wiring

Malfunctioning components (such as sticking
relays, solenoids, etc.)

EMI/RFI (Electromagnetic/radio frequency
interference)

Aftermarket equipment
Intermittent diagnosis requires careful analysis of
suspected systems to help prevent replacing good
parts. This may involve using creativity and ingenuity to
interpret customer complaints and simulating all
external and internal system conditions to duplicate the
problem.

3.5L ENGINE DRIVEABILITY AND EMISSIONS 6E-67
What you should do
Step 1: Acquire information
A thorough and comprehensive customer check sheet
is critical to intermittent problem diagnosis. You should
require this, since it will dictate the diagnostic starting
point. The vehicle service history file is another
source for accumulating information about the
complaint.

Step 2: Analyze the intermittent problem
Analyze the customer check sheet and service history
file to determine conditions relevant to the suspect
system(s).
Using service manual information, you must identify,
trace and locate all electrical circuits related to the
malfunctioning system(s). If there is more than one
system failure, you should identify, trace and locate
areas of commonality shared by the suspect circuits.

Step 3: Simulate the symptom and isolate the
problem
Simulate the symptom and isolate the system by
reproducing all possible conditions suggested in Step 1
while monitoring suspected circuits/components
/
systems to isolate the problem symptom. Begin with the
most logical circuit/component.
Isolate the circuit by dividing the suspect system into
simpler circuits. Next, confine the problem into a smalle
r
area of the system. Begin at the most logical point (or
point of easiest access) and thoroughly check the
isolated circuit for the fault, using basic circuit tests.

Hints
You can isolate a circuit by:

Unplugging connectors or removing a fuse to
separate one part of the circuit from another

If only component fails to operate, begin testing
the component

If a number of components do not operate, begin
test at areas of commonality (such as powe
r
sources, ground circuits, switches, main
connectors or major components)

Substitute a known good part from the parts
department or the vehicle system

Try the suspect part in a known good vehicle See
Symptom Simulation Tests on the next page fo
r
problem simulation procedures. Refer to service
manual sections 6E and 8A for information abou
t
intermittent diagnosis. Follow procedures for basic
circuit testing in service manual section 8A.
What resources you should use
Whenever appropriate, you should use the following
resources to assist in the diagnostic process:

Service manual

Bulletins

Digital multimeter (with a MIN/MAX feature)

Tech 2 and Tech 2 upload function

Circuit testing tools (including connecto
r
kits/harnesses and jumper wires)

Experience

Intermittent problem solving simulation methods

Customer complaint check sheet
Symptom Simulation Tests
1. Vibration
This method is useful when the customer complain
t
analysis indicates that the problem occurs when the
vehicle/system undergoes some form of vibration.
For connectors and wire harness, slightly shake
vertically and horizontally. Inspect the connector join
t
and body for damage. Also, tapping lightly along a
suspected circuit may be helpful.
For parts and sensors, apply slight vibration to the par
t
with a light tap of the finger while monitoring the system
for a malfunction.
2. Heat
This method is important when the complaint suggests
that the problem occurs in a heated environment. Apply
moderate heat to the component with a hair drier o
r
similar tool while monitoring the system for a
malfunction.
CAUTION: Care must be take to avoid overheating
the component.
3. Water and Moisture
This method may be used when the complaint suggests
that the malfunction occurs on a rainy day or unde
r
conditions of high humidity. In this case, apply water in
a light spray on the vehicle to duplicate the problem.
CAUTION: Care must be take to avoid directly
exposing electrical connections to water.
4. Electrical loads
This method involves turning systems ON (such as the
blower, lights or rear window defogger) to create a load
on the vehicle electrical system at the same time you
are monitoring the suspect circuit/component.

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 -101

NO CHECK ENGINE LAMP (MIL)

RTW46EM F000401

CIRCUIT DESCRIPTION
The “Check Engine" lamp (MIL) should always be
illuminated and steady with the ignition “ON" and the
engine stopped. Ignition feed voltage is supplied to the
MIL bulb through the meter fuse. The Engine Control
Module (ECM) turns the MIL “ON" by grounding the MIL
driver circuit.

DIAGNOSTIC AIDS
An intermittent MIL may be cased by a poor connection,
rubbed-through wire insulation, or a wire broken inside
the insulation. Check for the following items:

Inspect the ECM harness and connections fo
r
improper mating, broken locks, improperly formed o
r
damaged terminals, poor terminal-to-wire connection,
and damaged harness.

If the engine runs OK, check for a faulty light bulb, an
open in the MIL driver circuit, or an open in the
instrument cluster ignition feed.
 If the engine cranks but will not run, check for an
open ECM ignition or battery feed, or a poor ECM to
engine ground.

6E-102 3.5L ENGINE DRIVEABILITY AND EMISSIONS

No Check Engine Lamp (MIL)

Step
Action Value (s) Yes No
1
Check the meter fuse (15A). If the fuse is burnt out,
repair as necessary.
Was the problem found?
- Verify repair Go to Step 2

2
Using the DVM and check the "CHECK ENGINE"
lamp circuit.
1. Ignition "Off", engine "Off".
2. Disconnect the ECM connector.
3. Ignition "On".
4. Check the circuit for open circuit.
Was the DVM indicated specified value?
V
E-61(B)



10 – 14.5V
Go to Step 5

Go to Step 3

3
Check the "CHECK ENGINE" lamp bulb. If the bulb is
burnt out, repair as necessary.
Was the problem found?
- Verify repair Go to Step 4

4
Using the DVM and check the "CHECK ENGINE"
lamp circuit.
1. Ignition "Off", engine "Off".
2. Disconnect the meter connector and ECM
connector.
3. Check the circuit for open circuit.
Was the problem found?




E-61(B)
B-24


-
Verify repair
Go to Step 5

5
Is the ECM programmed with the latest software
release?
If not, download the latest software to the ECM using
the "SPS (Service Programming System)"
.
Was the problem solved?
-
Verify repair
Go to Step 6

6E-112 3.5L ENGINE DRIVEABILITY AND EMISSIONS
CAUTION: To reduce the risk of fire and personal
injury:
 It is necessary to relieve fuel system pressure
before connecting a fuel pressure gauge. Refer to
Fuel Pressure Relief Procedure, below.
 A small amount of fuel may be released when
disconnecting the fuel lines. Cover fuel line
fittings with a shop towel before disconnecting,
to catch any fuel that may leak out. Place the
towel in an approved container when the
disconnect is completed.
FUEL PRESSURE RELIEF PROCEDURE
1. Remove the fuel cap.
2. Remove the fuel pump relay from the underhood
relay center.
3. Start the engine and allow it to stall.
4. Crank the engine for an additional 3 seconds.
FUEL GAUGE INSTALLATION
1. Remove the fuel pressure fitting cap.
2. Install fuel gauge 5-8840-0378-0 to the fuel feed line
located in front of and above the right side valve
cover.
3. Reinstall the fuel pump relay.

Fuel System Electrical Test
Step Action Value (s) Yes No
1
Was the "On-Board Diagnostic (OBD) System Check"
performed?
- Go to Step 2 Go to On Board
Diagnostic (OBD)
System Check
2
1. Using the Tech 2, ignition "On" and engine "On".
2. Select the "Miscellaneous Test" and perform the
"Fuel Pump Relay" in the "Relays".
3. Operate the Tech 2 in accordance with procedure.
Was the fuel pump operated, when the Tech 2 is
operated?
- Test completed Go to Step 3
3
Check the "Fuel Pump" fuse (20A). If the fuse is burnt
out, repair as necessary.
Was the problem found?
- Verify repair Go to Step 4
4
Check for poor/faulty connection at the fuel pump, fuel
pump relay or ECM connector. If a poor/faulty
connection is found, repair as necessary.
E-61(B)
X-2


F-2
C-109










Was the problem found?
- Verify repair Go to Step 5