2004 ISUZU TF SERIES ABS

ENGINE DIAGNOSIS (C24SE) 6-5
Rough Engine Running
Condition Possible cause Correction
Engine misfires regularly Ignition coil layer shorted Replace
Spark plugs fouling Clean or install hotter type plug
Spark plug(s) insulator nose
leaking Replace
Spark plug wire incorrect Connect properly or replace
Fuel injector(s) defective Replace
Engine control module faulty Replace
Engine knocks regularly Spark plugs running too hot Install colder type spark plugs
Powertrain control module faulty Replace
Engine lacks power Spark plugs fouled Clean
Spark plug wire incorrect Connect properly or replace
Fuel injectors defective Replace
Manifold Absolute Pressure
(MAP)
Sensor or Manifold Absolute
Pressure Sensor circuit defective Correct or replace
Engine Coolant Temperature
Sensor or Engine Coolant
Temperature Sensor circuit
defective Correct or replace
Engine Control Module faulty Replace
Intake Air Temperature Sensor or
Intake Air Temperature Sensor
circuit defective Correct or replace
Throttle Position Sensor or
Throttle Position Sensor circuit
defective Correct or replace
Knock Sensor or Knock Sensor
circuits defective Correct or replace
Knock Sensor Module or Knock
Sensor Module circuits defective Correct or replace

6-6 ENGINE DIAGNOSIS (C24SE)
Hesitation
Condition Possible cause Correction
Hesitation on acceleration Throttle Position Sensor
adjustment incorrect Replace throttle valve assembly
Throttle Position Sensor circuit
open or shorted Correct or replace
Excessive play in accelerator
linkage Adjust or replace
Manifold Absolute Pressure
(MAP) Sensor circuit open or
shorted Correct or replace
MAP Sensor defective Replace
Intake Air Temperature (IAT)
Sensor circuit open or shorted Correct or replace
Knock Sensor (KS) Circuit open or
shorted Correct or replace
KS defective Replace
KS Module circuits open or
shorted Correct or replace
KS Module defective Replace
IAT Sensor defective Replace
Hesitation at high speeds
(Fuel pressure too low) Fuel tank strainer clogged Clean or replace
Fuel pipe clogged Clean or replace
Fuel filter clogged Replace
Defective fuel pump system Check and replace
Fuel Pressure Control Valve
leaking Replace
Hesitation at high speeds
(Fuel injector not working
normally) Power supply or ground circuit for
Multiport Fuel Injection System
shorted or open Check and correct or replace
Cable of Multiport Fuel Injection
System disconnected or defective Correct or replace
Hesitation at high speeds Engine Control Module defective Replace
Throttle Position Sensor circuit
open or shorted Correct or replace
Throttle Position Sensor defective Replace
Engine Coolant Temperature
Sensor circuit open or shorted Correct or replace
Engine Coolant Temperature
Sensor defective Replace
MAP Sensor cable open or
shorted Correct or replace
MAP Sensor defective Replace
IAT Sensor circuit open or shorted Correct or replace
IAT Sensor defective Replace
KS Circuit open or shorted Correct or replace
KS defective Replace
KS Module circuit open or shorted Correct or replace
KS Module defective Replace
Throttle valve not wide opened Check and correct or replace
Air Cleaner Filter clogged Replace filter element
Power supply voltage too low Check and correct or replace

ENGINE DIAGNOSIS (C24SE) 6-7
Engine Lacks Power
Condition Possible cause Correction
Trouble in fuel system Fuel Pressure Control Valve not
working normally Replace
Fuel injector clogged Clean or replace
Fuel pipe clogged Clean
Fuel filter clogged or fouled Replace
Fuel pump drive circuit not
working normally Correct or replace
Fuel tank not sufficiently breathing
due to clogged Evaporative
Emission Control System circuit Clean or replace
Water in fuel system Clean
Inferior quality fuel in fuel system Use fuel of specified octane rating
Engine Control Module supplied
poor voltage Correct circuit
Throttle Position Sensor cable
disconnected or broken Correct or replace
Throttle Position Sensor defective Replace
Manifold Absolute Pressure
Sensor not working normally Replace
Intake Air Temperature sensor not
working normally Replace
Engine Coolant Temperature
Sensor circuit open or shorted Correct or replace
Engine Coolant Temperature
Sensor defective Replace
Engine Control Module defective Replace
Trouble in intake or exhaust
system Air Cleaner Filter clogged Replace filter element
Air duct kicked or flattened Correct or replace
Ignition failure
- Refer to Hard Start
Troubleshooting Guide
Heat range of spark plug
inadequate Install spark plugs of adequate
heat range
Electronic Ignition System with
module Replace

ENGINE DIAGNOSIS (C24SE) 6-11
Abnormal Combustion
Condition Possible cause Correction
Trouble in fuel injection system Fuel pressure control valve
defective Replace
Fuel filter clogged Replace
Fuel pump clogged Clean or replace
Fuel tank or fuel pipe clogged Clean or replace
Fuel injector clogged Clean or replace
Fuel pump relay defective Replace
Power supply cable for fuel pump
loosely connected or defective Reconnect, correct or replace
Manifold Absolute Pressure
Sensor circuit open or shorted Correct or replace
Manifold Absolute Pressure
Sensor defective Replace
Engine Coolant Temperature
(ECT) Sensor circuit open or
shorted Correct or replace
ECT Sensor defective Replace
Throttle Position Sensor
adjustment incorrect Reconnect
Throttle Position Sensor defective Replace
Throttle Position Sensor
connector loosely connected Reconnect
Vehicle Speed Sensor cable
loosely connected or defective Correct or replace
Vehicle Speed Sensor loosely
fixed Fix tightly
Vehicle Speed Sensor in wrong
contact or defective Replace
Engine Control Module cable
loosely connected or defective Correct or replace
Trouble in emission control
system Heated Oxygen Sensor circuit
open (If applicable) Correct or replace
Heated Oxygen Sensor defective
(If applicable) Replace
Signal vacuum hose loosely fitted
or defective Correct or replace
ECT Sensor circuit open or
shorted Correct or replace
ECT Sensor defective Replace
Evaporative Emission Control
system (If applicable) Refer to Section 6E
Trouble in ignition system - Refer to "Engine Lacks Power"
Trouble in cylinder head parts Carbon deposits in combustion
chamber Remove carbon
Carbon deposit on valve, valve
seat and valve guide Remove carbon

6-14 ENGINE DIAGNOSIS (C24SE)
Malfunction Indicator Lamp
The instrument panel "CHECK ENGINE" Malfunction
Indicator lamp (MIL) illuminates by self diagnostic
system when the system checks the starting of
engine, or senses malfunctions.

Condition Possible cause Correction
"CHECK ENGINE" MIL does not
illuminate at the starting of engine Bulb defective Replace
MIL circuit open Correct or replace
Command signal circuit to operate
self diagnostic system shorted Correct or replace
Engine Control Module (ECM)
cable loosely connected,
disconnected or defective Correct or replace
ECM defective Replace
“CHECK ENGINE” MIL
illuminates, and stays on Deterioration heated oxygen
sensor of internal element Replace
Heated oxygen sensor connector
terminal improper contact
(If applicable) Reconnect properly
Heated oxygen sensor lead wire
shorted (If applicable) Correct
Heated oxygen sensor circuit
open (If applicable) Correct or replace
Deterioration engine coolant
temperature sensor of internal
element Replace
Engine coolant temperature
sensor connector terminal
improper contact Reconnect properly
Engine coolant temperature
sensor lead wire shorted Correct
Engine coolant temperature
sensor circuit open Correct or replace
Throttle position sensor open or
shorted circuits Correct or replace
Deterioration of crankshaft
position sensor Replace
Crankshaft position sensor circuit
open or shorted Correct or replace
Vehicle speed sensor circuit open Correct or replace
Manifold absolute pressure sensor
circuit open or shorted Correct or replace
Intake air temperature sensor
circuit open or shorted Correct or replace
Fuel injector circuit open or shorted Correct or replace
ECM driver transistor defective Replace EPROM or ECM
Malfunctioning of ECM RAM
(Random Access Memory) or
Malfunctioning of ECM PROM
(Programmed Read Only Memory)Replace EPROM or ECM

6A-72 ENGINE MECHANICAL (C24SE)
FUEL INJECTOR



Removal
Caution: To reduce the risk of fire and personal injury, it is
necessary to relieve the fuel system pressure before
servicing the fuel system components.

Caution: After relieving the fuel system pressure, a small
amount of fuel may be released when servicing fuel lines
or connections. Reduce the chance of personal injury by
covering the fuel line fitting with a shop towel before
disconnecting the fittings. The towel will absorb any fuel
that may leak out. When the disconnect is completed,
place the towel in an approved container.

1. Depressurize the fuel system.
2. Disconnect the fuel inlet.
3. Disconnect the fuel return line.
4. Remove the fuel rail from the intake manifold.
5. Remove the fuel injector from the fuel rail by disengaging
claws.

Installation
1. Install the fuel injector to the fuel rail by engaging claws.
2. Install the fuel rail to the intake manifold.
3. Connect the fuel return line firmly.
4. Connect the fuel supply line firmly.





Knock sensor
Removal
1. Remove fixing bolts.
2. Disconnect the connector at the other side.


Tighten (Torque)
Oxygen sensor in exhaust pipe - 30N

m (3.2 kgf

m)
When re-using, insert oxygen sensor.

6C-4 ENGINE FUEL (C24SE)

Fuel Metering
Engine Control Module (ECM) is in complete control of this fuel
delivery system during normal driving conditions.
The intake manifold function, like that of a diesel, is used only
to let air into the engine. The fuel is injected by separate
injectors that are mounted over the intake manifold.
The Manifold Absolute Pressure (MAP) sensor measures the
changes in the intake manifold pressure which result from
engine load and speed changes, which the MAP senso
r
converts to a voltage output.
This sensor generates the voltage to change corresponding to
the flow of the air drawn into the engine.
The changing voltage is transformed into an electric signal and
provided to the ECM.
With receipt of the signals sent from the MAP sensor, Intake
Air Temperature sensor and others, the ECM determines an
appropriate fuel injection pulse width feeding such information
to the fuel injector valves to effect an appropriate air/fuel ratio.
The Multiport Fuel Injection system utilizes an injection system
where the injectors turn on at every crankshaft revolution. The
ECM controls the injector on time so that the correct amount o
f
fuel is metered depending on driving conditions.
Two interchangeable "O" rings are used on the injector tha
t
must be replaced when the injectors are removed.
The fuel rail is attached to the top of the intake manifold and
supplies fuel to all the injectors.
Fuel is recirculated through the rail continually while the engine
is running. This removes air and vapors from the fuel as well
as keeping the fuel cool during hot weather operation.
The fuel pressure control valve that is mounted on the fuel rail
maintains a pressure differential across the injectors under all
operating conditions. It is accomplished by controlling the
amount of fuel that is recirculated back to the fuel tank based
on engine demand.
See Section "Driveability and Emission" for more information
and diagnosis.

6D2-2 IGNITION SYSTEM



General Description
Ignition is done by the Ignition Module that fires.
Since the cylinder on exhaust stroke requires less energy to
fire its spark plug, energy from the ignition coils can be utilized
to fire the mating cylinder on compression stroke.
A notch in the timing disc on the crankshaft activates the crank
angle sensor which then sends information such as firing order
and starting timing of ignition coil to the ECM.
By receiving signals such as crank position, engine speed,
water temperature and Manifold Absolute Pressure (MAP), the
ECM controls the ignition timing.




Service Precaution
CAUTION:
Always use the correct fastener in the proper location.
When you replace a fastener, use ONLY the exact part
number for that application. ISUZU will call out those
fasteners that require a replacement after removal. ISUZU
will also call out the fasteners that require thread lockers
or thread sealant. UNLESS OTHERWISE SPECIFIED, do
not use supplemental coatings (Paints, greases, or other
corrosion inhibitors) on threaded fasteners or fastener
joint interfaces. Generally, such coatings adversely affect
the fastener torque and the joint clamping force, and may
damage the fastener. When you install fasteners, use the
correct tightening sequence and specifications. Following
these instructions can help you avoid damage to parts
and systems.




Diagnosis
Refer to Section Drivability and Emissions for the diagnosis to
electronic ignition system (El system).





Ignition Coil
Removal
1. Disconnect battery ground cable.
2. Disconnect the Ignition coil connector.
3. Remove the ignition coil.



Installation
1. Install the ignition coil.
Connect ignition coil connector and ignition coil, then tighten
bolt to the specified torque.
Torque: 20 N




m (2.0 kgf




m)
2. Connect battery ground cable.