Isuzu 4HL1 Instruction manual

WORKSHOP MANUAL
727 (N SERIES)
ENGINE CONTROL SYSTEM
(4HL1 ENGINE)
SECTION 1A
International Service & Parts
Tokyo, Japan

N O T I C E
Before using this Workshop Manual to assist you in performing
vehicle service and maintenance operations, it is recommended
that you carefully read and thoroughly understand the information
contained in Section - 0A under the headings “GENERAL REPAIR
INSTRUCTIONS” and “HOW TO USE THIS MANUAL”.
All material contained in this Manual is based on the latest product
information available at the time of publication.
All rights are reserved to make changes at any time without prior
notice.

Engine Control System 1A-1
ENGINE
Engine Control System
CONTENTS
Engine Control System . . . . . . . . . . . . . . . . . . . . 1A-2
Precautions on Service . . . . . . . . . . . . . . . . . . 1A-2
Function and Operation . . . . . . . . . . . . . . . . . . 1A-3
Powertrain System Components . . . . . . . . . . . 1A-9
Circuit Diagram . . . . . . . . . . . . . . . . . . . . . . . 1A-20
Strategy-Based Diagnostics . . . . . . . . . . . . . . 1A-38
Functional Check List . . . . . . . . . . . . . . . . . . . 1A-44
Hearing Diagnostic . . . . . . . . . . . . . . . . . . . . . 1A-44
On-Board Diagnostic (OBD) System Check . 1A-47
Inactive CHECK ENGINE Lamp Check . . . . . 1A-50
Unblinking CHECK ENGINE Lamp Check . . . 1A-54
ECM Power Supply and Grounding System Circuit
Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-56
Diagnosis with Tech 2 Scan Tool . . . . . . . . . . 1A-59
Diagnostic Chart . . . . . . . . . . . . . . . . . . . . . . . 1A-88
DTC14 - CMP Sensor System Fault . . . . . . . 1A-93
DTC15 - CKP Sensor System Fault . . . . . . . . 1A-97
DTC18 - Starter Degradation (For Only Vehicles
Equipped with Idle Stop Function) . . . . . . . . 1A-101
DTC22 - IAT Sensor System Fault . . . . . . . . 1A-103
DTC23 - ECT Sensor System Fault . . . . . . . 1A-107
DTC24 - Accelerator Sensor System Fault . 1A-112
DTC25 - Vehicle Speed Sensor System
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-116
DTC28 - PTO Accelerator Sensor System
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-120
DTC31 - Idle Up Volume System Fault . . . . 1A-123
DTC33 - VIM Internal Fault (EEPROM Write
Error) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-127
DTC34 - ECM Internal Fault (Charge Circuit
Fault) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-129
DTC35 - VIM Internal Fault (A/D Conversion
Fault) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-132
DTC43 - ITP Sensor System Fault . . . . . . . . 1A-134
DTC44 - EGR Valve Position Sensor System
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-139
DTC45 - EGR Valve System Fault . . . . . . . . 1A-144
DTC46 - Exhaust Brake System Fault . . . . . 1A-147
DTC51 - ECM Internal Fault (CPU Error / CPU
History Error) . . . . . . . . . . . . . . . . . . . . . . . . 1A-150
DTC52 - ECM Internal Fault
(Sub CPU Error) . . . . . . . . . . . . . . . . . . . . . . 1A-152
DTC61 - Intake Throttle Valve System Fault 1A-154
DTC71 - Barometric Pressure Sensor Fault 1A-157
DTC81 - Clutch Switch System Fault . . . . . . 1A-159
DTC82 - Neutral Switch System Fault . . . . . 1A-163
DTC84 - CAN Communication Fault
(CAN Bus Error) . . . . . . . . . . . . . . . . . . . . . . 1A-166
DTC86 - CAN Communication Fault
(CAN Timeout Error) . . . . . . . . . . . . . . . . . . . 1A-169
DTC115 - Common Rail Pressure Sensor Fixed
Output Fault . . . . . . . . . . . . . . . . . . . . . . . . . 1A-172
DTC118 - Common Rail Pressure Fault
(Control System) . . . . . . . . . . . . . . . . . . . . . 1A-177
DTC158 - Injector Power Supply System Short
(Common 1) . . . . . . . . . . . . . . . . . . . . . . . . . 1A-182
DTC159 - Injector Power Supply System Short
(Common 2) . . . . . . . . . . . . . . . . . . . . . . . . . 1A-186
DTC211 - Fuel Temperature Sensor System
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-190
DTC217 - SCV Drive System Short . . . . . . . 1A-195
DTC227 - No Pump Pressure Feed (Fuel Leak)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-198
DTC241 - Idle Position Switch Circuit Open
Wiring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-203
DTC242 - Idle Position Switch Circuit Short . 1A-206
DTC245 - Common Rail Pressure Sensor
System Fault . . . . . . . . . . . . . . . . . . . . . . . . 1A-209
DTC247 - SCV Drive System Fault . . . . . . . 1A-215
DTC271 - Cylinder 1 (Injector Drive System)
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-219
DTC272 - Cylinder 2 (Injector Drive System)
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-223
DTC273 - Cylinder 3 (Injector Drive System)
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-227
DTC274 - Cylinder 4 (Injector Drive System)
Fault . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-231
DTC277 - Injector Power Supply System Open
Wiring Fault (Common 1) . . . . . . . . . . . . . . . 1A-235
DTC278 - Injector Power Supply System Open
Wiring Fault (Common 2) . . . . . . . . . . . . . . . 1A-239
DTC416 - Main Relay System Fault . . . . . . . 1A-243
DTC417 - Starter Switch System Fault . . . . 1A-246
DTC543 - High Engine Speed Error . . . . . . . 1A-249
Default Matrix Table . . . . . . . . . . . . . . . . . . . 1A-250
Special Tools . . . . . . . . . . . . . . . . . . . . . . . . 1A-256
Wiring Harness Repair: Shielded Cable . . . . . 1A-257
Removal Procedure . . . . . . . . . . . . . . . . . . . 1A-257
Installation Procedure . . . . . . . . . . . . . . . . . 1A-257
Twisted Leads . . . . . . . . . . . . . . . . . . . . . . . . . 1A-258
Removal Procedure . . . . . . . . . . . . . . . . . . . 1A-258
Installation Procedure . . . . . . . . . . . . . . . . . 1A-258
Weather-Pack Connector . . . . . . . . . . . . . . . . 1A-260
Removal Procedure . . . . . . . . . . . . . . . . . . . 1A-260
Installation Procedure . . . . . . . . . . . . . . . . . 1A-260
Special Tools . . . . . . . . . . . . . . . . . . . . . . . . 1A-261
Com-Pack III . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-262
General Information . . . . . . . . . . . . . . . . . . . 1A-262
Metri-Pack . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1A-263
Removal Procedure . . . . . . . . . . . . . . . . . . . 1A-263
Installation Procedure . . . . . . . . . . . . . . . . . 1A-263
Special Tools . . . . . . . . . . . . . . . . . . . . . . . . 1A-263

1A-2 Engine Control System
Engine Control System
Precautions on Service
Circuit test tools
Unless otherwise specified in diagnostic procedures,
do not use Test Light to diagnose the powertrain
electrical system. When diagnostic procedures need
probe connector, use Connector Test Adapter Kit 5-
8840-0385-0.
On-market electrical equipment and vacuum
devices
On-market electrical equipment and vacuum devices
refer to those components that will be installed to
vehicles after shipment from manufacturing plants. Be
careful that installation of these components is not
considered during the process of vehicle design.
CAUTION:
Do not install on-market vacuum devices to
vehicles.
CAUTION:
Connect on-market electrical equipment, as well as
its power supplies and grounds, to the circuits
isolated from the electronic control system.
The on-market electrical equipment, even when
installed to vehicles in normal manner, may bring
functional troubles to the electronic control system.
Affected devices include those not connected to the
vehicle electrical equipment system, for example,
mobile phones or radios. Therefore, when you intend to
diagnose the powertrain, check such the on-market
electrical equipment has not been installed to the
vehicle and, if installed, remove it. If faults still occur
even after removal of on-market electrical equipment,
diagnose the vehicle according to normal procedures.
Damage by electrostatic discharge
Electronic components used in the electronic control
system are designed to work at very low voltages and,
for this reason, they are susceptible to damage by
electrostatic discharge and some types of electronic
components may be damaged even by the static
electricity of less than 100 V that is usually not sensed
by persons. Persons’ sensitivity level is 4,000 V.
Persons are electrostatically charged in various ways
and the most typical electrification sources are friction
and induction. Shown below are examples.
• Electrification by friction occurs when a person
slides on the seat in the vehicle.
• Electrification by induction occurs when a person
with insulating shoes is standing near a highly
electrifiable substance and touches a ground
momentarily. Electric charges with the same
polarity flow out and resultantly the person is
charged at high opposite polarity. Since static
electric charges cause damages, it is important
when you handle or test electronic components.
CAUTION:
To prevent damages by electrostatic discharge,
follow the guidelines shown below.
• Do not touch ECM connector pins as well as
electronic components soldered to the ECM
circuit board.
• Do not unpack each replacement component
until preparations are completed for the
component.
• Before taking out a component from the
package, connect the package to the normal
grounding line of the vehicle.
• When you intend to slide on the seat, change
the posture from standing to sitting, or walk by
a certain distance to handle a component,
touch an appropriate grounding material.
Wire color
All wiring harnesses are identified using colored jacket.
The wiring harness used for the main circuit in an
electrical system is identified with single color while the
wiring harness used for the sub-circuit is identified with
color stripe. The following rule is used in each wiring
diagram to indicate size and color of a wiring harness.
Legend
1. Red (stripe color)
2. Green (base color)
3. Harness size (0.5 mm2)
LNW21ASH000101-X
eg. : 0.5 GRN / RED
1
2
3

Engine Control System 1A-3
Function and Operation
Electronic Control System
The electronic control system processes the data,
which has been collected with various types of sensors,
by means of the control program installed to ECM
(engine control module) to totally control engine
parameters such as fuel injection quantity, injection
timing, engine startup, altitude compensation, and
EGR.
ECM
ECM Description
The ECM is mounted in the inner part of the engine left
side cover. The ECM monitors various data sent from
diversified sensors and controls systems in the
powertrain. The ECM diagnoses these systems to
detect faults with respect to system operations and
inform the driver of faulty condition via the CHECK
ENGINE lamp (MIL) and stores DTCs (diagnostic
trouble codes). DTC identifies the trouble generation
area to aid repairs by service operators.
Function of ECM
ECM supplies 5 V and 12 V voltages to various sensors
and switches. Since powers are supplied via high
resistances in ECM, Test Light, even when connected
to the circuit, will not be lit. In a special case, a normal
voltmeter does not indicate correct values since the
resistance of the instrument is too low. To get accurate
readings, you need a digital voltmeter whose input
impedance is at least 10 MΩ. The special tool 5-8840-
0366-0 is a proper choice for this measurement. In the
ECM, the output circuit is controlled by regulating the
grounding system or power circuit via transistor or
either of the devices listed below.
• Output driver module (ODM)
• Quad drive module (QDM)
ECM and Components
The ECM is designed to offer excellent drivability and
fuel economy while achieving exhaust gas emission
control requirements. The ECM monitors engine and
vehicle functions via various electronic sensors such as
CKP (crank position) and VS (vehicle speed) sensors.
Voltages from ECM
The ECM supplies reference voltages to various
switches and sensors. Resistances of the ECM are
very high and this allows the ECM to supply voltages to
these devices, and voltages actually applied to circuits
are low and even connecting Test Light to individual
circuits may fail turn-on. Since the voltmeter normally
used in service factories has low input impedance,
correct readings may not be obtained. To get accurate
readings, a digital voltmeter whose input impedance is
10 MΩ(for example, 5-8840-0366-0) should be used.
Input/output devices of the ECM include analog-to-
digital converter, signal buffer, counter, and special
driver. By using electronic switches, the ECM controls
most system components and turning off a switch
closes the ground circuit. These switches are divided
into four-switch or seven-switch groups, and the former
group is called quad driver module (QDM) and controls
up to four output pins respectively while the latter group
is called output driver module (ODM) and controls up to
seven outputs respectively. Note that all the outputs are
necessarily not used in the control.
Electrically Erasable Programmable ROM
(EEPROM)
EEPROM is a permanent memory chip and soldered to
the board in the ECM. EEPROM stores program and
calibration data, both of which are necessary for the
ECM to control the powertrain. Different from
conventional ROMs, EEPROM cannot be replaced with
new component. If EEPROM fails, the complete ECM
assembly must be replaced with new one.
Precautions on ECM Service
The ECM is designed to withstand ordinary currents
used in operations of a vehicle. Be careful that the
circuits must not be overloaded. To test the ECM to
check open wiring or short, ECM circuits must be
connected to the ground or voltages must not be
applied to the ECM. To test ECM circuits, the digital
voltmeter 5-8840-0366-0 should always be used.
Symbol Color Symbol Color
BBlackBRBrown
W White LG Light green
R Red GR Gray
GGreenP Pink
Y Yellow LB Light blue
L Blue V Violet
OOrange

1A-4 Engine Control System
Engine Control System
The engine control system comprehends vehicle status
and driver’s intention based on the data acquired from
sensors and switches to adapt the engine to changing
situation so that the vehicle will achieve optimal running
condition. The heart of the engine control system is
ECM and this device provides direct control tasks for
the engine system, including fuel injection control,
intake throttle control, EGR control, and QWS control.
The ECM also governs vehicle system control
strategies such as exhaust brake control and idle stop
control via VIM. In addition, the ECM communicates
with other key systems, including ABS/ASR system
and clutch free system, via VIM.
LNW21ALF004601-X
Switch
A/C switch
Relay/Lamp
Starter cut relay
Glow relay
Check engine lamp
Tachometer
TCM
ABS/ASR ECU
ISS ECU
Vehicle functions
Atomospheric
pressure sensor
VIM
(Vehicle Interface Module)
ECM
(Engine Control Module)
Relay
ECO Relay,
Exhaust Brake
Idle
Idle Up Volume
Others
Freezer Switch
Clean Starting Memory
QWS Switch
Lamp
Exhaust Brake Lamp
Glow Lamp
Brake
Stop Lamp Relay
Exhaust Brake Lamp
Power Take OFF (PTO)
Quick Warm Up System
PTO Switch (
ACTIVE HIGH )
PTO Switch (
ACTIVE LOW )
PTO Accelerator Sensor
Transmission
Clutch Switch
Neutral Switch (MT)
Parking
/Neutral (AT)
Switch
Vehicle Speed Sensor
Accelerator
AP sensor
Idle position switch CAN
Main relay
IAT sensor
Exhaust brake
solenoid valve
Battery +
Starter
Outer diagnostic unit
Battery
Ignition switch
Starter switch
Diagnostic switch
Common rail
pressure sensor
SCV
FT sensor
Injector
EGR valve drive
EGR cooler
Exhaust
pipe
Supply
pump
EGR valve position sensor
CMP sensor
ITP sensor
Intake throttle drive
ECT
Common rail
CKP

Engine Control System 1A-5
Fuel Injection Control
The fuel injection control system manages the injection
quantity, injection timing, and injection pressure
according to the status of vehicle. This system changes
the injection quantity using injector operating period,
the injection timing using injector operation timing, and
the injection pressure using SCV drive duty,
respectively. The fuel injection consists of two stages,
pilot injection and main injection, and the control
system changes the amount and timing in individual
stages according to the conditions encountered.
The ECM uses the data acquired from associated
sensors and switches to judge the current vehicle
status, i.e., startup, idling, PTO, or idle stop, and
calculate the desired injection quantity. Once the
desired injection quantity is determined, ECM
calibrates the value to determine injector energize time,
energize timing, and SCV opening and controls
injectors and the SCV accordingly.
Calculation of Desired Injection Quantity
The ECM calculates the basic injection quantity using
engine speed, accelerator pedal position, engine
coolant temperature, and other necessary parameters
and calibrates this value based on the atmospheric
pressure or the like to determine the desired injection
quantity.
Injector Control
The injector control consists of four stages: "control
stop mode" where the fuel injection is completely
stopped, "split injection mode" where two (or more)
injection shots are made for one cylinder at low engine
speeds and temperatures, "fixed injection mode" where
only main injection is made at very low engine speeds
during startup, and "normal injection mode" where the
fuel injection is made within normal engine speed
range. The proper mode is selected according to such
the parameters as engine speed, engine coolant
temperature, and DTC. The ECM uses the desired
injection quantity, intake air temperature, engine
coolant temperature, and other parameters to
determine injector energize period (desired injection
period) and injector energize timing (desired injection
timing) and control injectors according to the injection
mode selected.
SCV Control (Pump Control)
Pumps are controlled in six stages: "shutoff mode",
"start mode", "wait mode", "restart mode", "feedback
mode", and "deflate mode". The proper mode is
selected according to such the parameters as key
switch position, common rail pressure, and engine
speed. The ECM calculates desired injection pressure
and pump flow rate for the selected mode based on
intake air temperature, engine coolant temperature,
engine speed, desired injection quantity, and other
necessary parameters. Then, the ECM determines the
SCV opening (SCV drive duty) using these results and
controls the SCV.
ECM
DTC Detection Status
Battery Voltage
Key Switch Position
Engine Speed
Vehicle Speed
Engine Coolant Temp.
Status Judge Desired Injection
Quantity
Determine
Injector
Energize Time/
Timing Determine
SCV Position
Determine
Injector
Control
SCV
Control
Intake Air Temp.
Fuel Temp.
Accelerator Pedal Position
Idle Position Switch
Clutch Switch
Neutral Switch
PTO Switch
LNW21AMF005601-X
Compensation
Compensation
Compensation
Common Rail Pressure
Idle Stop

1A-6 Engine Control System
Intake Throttle Control
Legend
1. Intake throttle valve
2. ITP (intake throttle position) sensor 3. Intake throttle DC motor
The intake throttle control system changes (throttles)
the air according to the vehicle status and reduces
suction noises generated from the working exhaust
brake and acceleration. This control is made by
opening and closing the intake throttle valve. The
intake throttle valve is operated by the DC motor and
changing the drive voltage (duty: see Note 1) opens
and closes the valve. The intake throttle valve is fully
opened in the normal state (i.e., the DC motor is
inactive) and gradually reduces the opening as the
drive voltage is increased. The ECM uses the ITP
(intake throttle position) sensor to detect the working
condition of the intake throttle valve. When the valve
opening gets smaller (the drive voltage is increased),
the output voltage of the ITP sensor becomes lower.
The valve position is normally calculated using engine
coolant temperature, engine speed, and desired
injection quantity, and the DC motor drive voltage is
determined from this calculated value. However, the
ECM completely opens the throttle valve when the
vehicle is in idle stop, DTC is set for the intake throttle
system, AP sensor system, or EGR system, gear
shifting is performed (for manual transmission vehicle),
the engine coolant temperature is low (less than 70°C),
or the vehicle is in startup or engine stall status while it
completely closes the valve immediately after the key
switch is turned off (within 0.5 to 3.0 seconds).
There is an opposing relationship between intake
throttle control and EGR control. When the intake
throttle valve is opened, the EGR valve is closed, and
vice versa.
Note 1: Duty (%) = Energize ratio
LNW21AMF005701
3
1
2

Engine Control System 1A-7
EGR Control
Legend
1. EGR valve
2. EGR valve position sensor 3. EGR DC motor
The EGR control system recirculates a portion of
exhaust gas to the intake to drop the combustion
temperature and thus reduce NOx. This control is
made by opening and closing the EGR valve. The EGR
valve is operated by the DC motor and changing the
duty (see Note 1) opens and closes the valve. This
EGR valve is fully closed in the normal state (i.e., the
DC motor is inactive) and gradually enlarges the
opening as the duty is increased. The ECM uses the
EGR valve position sensor to comprehend the working
condition of the EGR valve. When the valve opening
gets larger (the duty is increased), the output voltage of
the EGR valve position sensor becomes higher.
The EGR control is initiated when parameters such as
engine speed, engine coolant temperature, accelerator
position, atmospheric pressure, and system voltage
meet the required conditions, and the EGR valve
opening is calculated from engine coolant temperature,
engine speed, and desired injection quantity. The ECM
determines the drive duty of the DC motor based on
this valve position and drives the motor. The EGR
control is turned off when the exhaust brake is
operated, the PTO is working, the AP sensor fails, the
ECT sensor fails, the EGR system fails, or the intake
throttle system fails.
There is an opposing relationship between EGR control
and intake throttle control. When the intake throttle
valve is opened, the EGR valve is closed, and vice
versa.
Note 1: Duty (%) = T (*) / 5 (msec) × 100
* T = Duty input time (see motor drive voltage
waveform)
Legend
1. 24V
2. 0V
3. T (duty input time)
4. 5 msec
LNW21AMF005801
3
2
1
1
2
3
4
LNW21ASH009101

1A-8 Engine Control System
QWS Control
The QWS (quick warm-up system) curtails the engine
warm-up time. The glow control covers the engine
warm-up during the period from pre-startup to
immediate completion of startup. The QWS works
when the vehicle meets the required conditions after
engine startup and the driver turns on the QWS switch,
and lasts until the vehicle deviates from the QWS
working conditions.
QWS working conditions
• The engine coolant is less than 73°C.
• The engine is running at or above 400 rpm for at
least 0.5 second.
• Both EGR and PTO controls are disabled.
• The vehicle is free from AP sensor fault, ECT
sensor fault, A/D conversion fault, idle position
switch fault, clutch switch fault, neutral switch fault,
and vehicle speed sensor fault.
• The difference between actual and desired engine
speeds is less than 50 rpm.
• The desired engine speed is less than 1000 rpm.
• The vehicle is being off.
• The state where the starter switch is turned off and
the idle position switch is turned on lasts for at
least 0.5 seconds.
Exhaust Brake Control
A valve is installed inside the exhaust pipe. Closing this
valve increases the resistance during the exhaust
stroke to enhance the effect of engine brake. The drive
source of the exhaust brake valve is vacuum. A
solenoid valve is installed to control the vacuum. The
exhaust brake is controlled by opening and closing this
solenoid electrically. When the engine is running at or
above 500 rpm, the exhaust cut command is not sent
from the automatic transmission, and exhaust brake or
QWS working conditions are completely met, the VIM
turns on the solenoid valve.
Exhaust Brake Working Conditions
• The vehicle is running at or above 5 km/h or faults
are not detected on the vehicle speed sensor.
• The exhaust brake switch is turned on.
• The engine is running at or above 500 rpm for at
least 1 second.
• The idle position switch is turned on and the gear
is engaged.
• The vehicle is not equipped with ABS/ASR or the
exhaust brake cut command is not sent from the
ASR.
• The vehicle is free from AP sensor fault, exhaust
brake circuit fault, clutch switch fault, neutral
switch fault, idle position switch fault, A/D
conversion fault (VIM), and CAN timeout (VIM).
• For a manual transmission vehicle, the clutch
pedal is not pressed. For an automatic
transmission vehicle, the exhaust brake command
is not sent from the automatic transmission.
• The system voltage stays between 20 V and 30 V.
Idle Stop Control (for Vehicles Equipped with Idle
Stop Control System)
The idle stop control system automatically cuts the
engine to prevent the black smoke emission from the
vehicle that is not running for unloading or other works
(to restart the engine, manual operation is needed).
When all the idle stop conditions are met, the ECM
stops fuel injection and actuates energy-saving relays
to turn off wipers, mirror defoggers, flashers, seat
heaters, and other electrical equipment.
Idle Stop Control Working Conditions
• The driver fails to apply the parking brake and the
signal is input from the alarm unit. (Note 1)
• The vehicle ran at or above 5 km/h.
• The vehicle is idling.
• The vehicle speed is 0 km/h.
• The shift lever is in the neutral position.
• The QWS switch is turned off.
• The engine coolant temperature is at least 10°C.
• The battery voltage is at least 22 V.
• DTC has not been detected.
Note 1: When all the following conditions are met, the
parking brake disengagement alarm unit outputs the
idle stop permit signal to the VIM.
• The idle stop main switch is turned on.
• The shift lever is in the neutral position.
• The parking brake is applied.
• The headlamps are turned off.
• Any of doors is opened.

Engine Control System 1A-9
Powertrain System Components
Component Layout - Vehicle Side
Legend
1. Engine
2. Neutral switch
3. ECM (engine control module)
4. VIM (vehicle interface module)
5. Clutch pedal
6. Accelerator pedal
7. DLC (data link connector)
8. CHECK ENGINE lamp (MIL)
9. Exhaust brake solenoid valve
10. VS (vehicle speed) sensor
LNW21AMF005501
65
7
1
8
4
3
210
9

1A-10 Engine Control System
Component Layout - Engine Side
Legend
1. ECT (engine coolant temperature) sensor
2. EGR valve
3. Intake throttle valve
4. CKP (crank position) sensor
5. FT (fuel temperature) sensor
6. SCV (suction control valve)
7. Common rail pressure sensor
8. CMP (cam position) sensor
Function and Operation
ECT Sensor The ECT (engine coolant temperature) sensor is
installed to the thermostat housing and the thermistor
in the sensor alters the resistance in response to the
temperature change. The resistance is decreased
when the coolant temperature is high while increased
when the temperature is low. The ECM supplies 5 V to
the ECT sensor via pull-up resistance and calculates
the engine coolant temperature from the change in
voltage and uses it in fuel injection control, EGR
control, and other control tasks. This voltage is
decreased when the resistance is large (the
temperature is high) while increased when the
resistance is large (the temperature is low).
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5
8
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Engine Control System 1A-11
EGR Valve and EGR Valve Position Sensor
The EGR valve is installed at the top of the inlet cover
and operated by a DC motor. The DC motor operates
the EGR valve by changing the duty. The valve is
opened when the duty is increased while closed when
the duty is decreased. The ECM calculates the desired
EGR valve opening based on the vehicle running
condition and controls the DC motor accordingly.
The EGR valve position sensor is installed to the EGR
valve and sends the voltage signal that will change in
response to the EGR valve opening to the ECM. The
ECM calculates the desired EGR valve opening from
the voltage signal and uses the result in EGR control.
Intake Throttle Valve and ITP Sensor
The intake throttle valve is installed to the intake throttle
and operated by a DC motor. The DC motor operates
the intake throttle valve by changing the drive voltage.
The valve is closed when the drive voltage is increased
while opened when the voltage is decreased. The ECM
calculates the intake throttle valve opening based on
the vehicle running condition and controls the DC
motor accordingly.
The ITP (intake throttle position) sensor is installed to
the intake throttle valve and sends the voltage signal
that will change in response to the throttle valve
opening to the ECM. The ECM calculates the throttle
valve opening from the voltage signal and uses the
result in intake throttle control.
CMP Sensor
The CMP (cam position) sensor is installed to each
cylinder head and, when the hole on the camshaft gear
passes the sensor, a CMP signal is generated. The
ECM identifies the cylinder from the CMP signal as well
as CKP signal sent from the CKP sensor and
determines the crank angle, and uses this angle in fuel
injection control and engine speed calculation. These
tasks are usually performed based on the CKP signal
but if the CKP sensor fails, the CMP signal will
substitute for the CKP signal.
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1A-12 Engine Control System
CKP Sensor
The CKP (crank position) sensor is installed to the
flywheel housing and, when flywheel teeth pass the
sensor, a CKP signal is generated. The ECM identifies
the cylinder from the CKP signal as well as the CMP
signal sent from the CMP sensor and determines the
crank angle, and uses this angle in fuel injection control
and engine speed calculation. These tasks are usually
performed based on the CKP signal but if the CKP
sensor fails, the CMP signal will substitute for the CKP
signal.
FT Sensor
The FT (fuel temperature) sensor is installed to the
supply pump and the thermistor in the sensor alters the
resistance in response to the temperature change. The
resistance is decreased when the fuel temperature is
high while increased when the temperature is low. The
ECM supplies 5 V to the FT sensor via pull-up
resistance and calculates the fuel temperature from the
change in voltage and uses it in supply pump control
and other control tasks. This voltage is decreased
when the resistance is small (the temperature is high)
while increased when the resistance is large (the
temperature is low).
SCV
The SCV (suction control valve) is installed to the
supply pump and controls the suction fuel quantity. The
SCV is fully opened in normal state and larger drive
voltage (duty) results in smaller opening. The ECM,
based on the data acquired from sensors, calculates
the desired common rail pressure and pump flow rate
and compares the calculated desired common rail
pressure to the actual value to determine the SCV
opening. When the actual pressure is lower than the
desired value, the SCV is opened to increase the pump
flow rate. When the actual pressure is higher than the
desired value, the SCV is closed to decrease the flow
rate.
Common Rail Pressure Sensor
The common rail pressure sensor is installed to the
supply pump, and detects the fuel pressure in the
common rail, converts the pressure into a voltage
signal, and sends the signal to the ECM. Higher
common rail pressure provides higher voltage while
lower pressure provides lower voltage. The ECM
calculates actual common rail pressure (fuel pressure)
from the voltage signal and uses the result in fuel
injection control and other control tasks.
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Engine Control System 1A-13
IAT Sensor
The IAT (intake air temperature) sensor is installed to
the intake air duct and the thermistor in the sensor
alters the resistance in response to the temperature
change. Higher intake air temperature provides smaller
resistance while lower intake air temperature provides
larger resistance. The ECM supplies 5 V to the IAT
sensor via pull-up resistance and calculates the intake
air temperature from the change in voltage and uses it
in fuel injection control and other control tasks. The
voltage is decreased when the resistance is small (the
temperature is high) while increased when the
resistance is large (the temperature is low).
AP Sensor
The AP (accelerator pedal position) sensor is installed
to the top of the accelerator pedal and supplies the
voltage signal that will change in response to
accelerator pedal angle to the ECM. The ECM
calculates the accelerator pedal position from the
voltage signal for use in fuel injection control and other
diversified control tasks.
Idle Position Switch
The idle position switch is installed to the accelerator
pedal, and is turned off when the pedal is pressed and
turned on when the pedal is released. The ECM
receives the on/off signal from this idle position switch
for use in exhaust brake control, warm-up control, and
other control tasks.
Clutch Switch
The clutch switch is installed to the clutch pedal, and is
turned on when the pedal is pressed and turned off
when the pedal is released. The VIM receives the on/
off signal from this clutch switch for use in exhaust
brake control and other control tasks.
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1A-14 Engine Control System
VS Sensor
The VS (vehicle speed) sensor is installed to the
transmission. The sensor is also equipped with a Hall
effect circuit. The magnet mounted to the transmission
output shaft is rotated together with the shaft to
generate a magnetic field. This Hall effect sensor
interacts with the magnetic field and generates and
sends a signal to the VIM. The VS sensor is energized
via meter fuse. The VIM uses VS signal pulses to judge
the vehicle speed.
Neutral Switch
The neutral switch (P/N switch in case of automatic
transmission) is installed to the transmission (shift lever
in case of automatic transmission), and is turned on
when the shift lever is moved to the neutral position.
The ECM receives the on/off signal from this neutral (or
P/N) switch to control the powertrain so that the driver
cannot start the engine as long as the shift lever is not
in the neutral (or parking) position.
Exhaust Brake Solenoid Valve
The exhaust brake solenoid valve is installed to the
rear of the right front wheel frame (some vehicle types
have different positions), and opens and closes the
vacuum path connected to the exhaust brake valve.
When this solenoid valve is turned on, the path is
opened and the vacuum is applied to the exhaust brake
valve. When the solenoid valve is turned off, the path is
closed and the atmospheric pressure is applied and
resultantly the exhaust brake valve is released. After
the exhaust brake switch is turned on and the vehicle
meets all the necessary conditions, the ECM turns on
the exhaust brake solenoid valve.
Atmospheric Pressure Sensor
The atmospheric pressure sensor is installed inside the
VIM and converts the atmospheric pressure into a
voltage signal. The VIM calculates the atmospheric
pressure from the voltage signal and sends the result to
the ECM. The ECM uses this atmospheric pressure to
calibrate the fuel injection quantity (altitude
compensation).
ECM
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Engine Control System 1A-15
The ECM is installed in the inner part of the engine left
side cover. The ECM uses signals sent from diversified
sensors to control those systems directly related to the
engine, for example, fuel injection control, intake
throttle control, EGR control, and QWS control.
VIM
The VIM is installed inside the center console in the
cab, and transmits signals sent from diversified
switches and sensors and drives powertrain actuators
such as exhaust brake, relays, and warning lamps
according to the commands from the ECM.
DLC
DLC (data link connector) is installed to the dash side
pane of the driver’s seat and acts as a communication
interface between external diagnostic tool and on-
board controllers. The DLC can also function as a
diagnostic switch and when DLC pins are shorted, this
diagnostic switch is turned on.
CHECK ENGINE Lamp (MIL)
The CHECK ENGINE lamp (MIL) is built in the meter
panel and informs the driver of faulty status of engine
or associated systems. When the ECM detects a fault
by means of its diagnostic function, this CHECK
ENGINE lamp is turned on. After the diagnostic switch
is turned on (DLC pins are shorted), the CHECK
ENGINE lamp blinks to inform the mechanic of
detection of DTC.
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1A-16 Engine Control System
Fuse Layout
Legend
1. Spare fuse
1
3
2
1
6
5
4
9
8
7
12
11
10
15
14
13
18
17
16
21
20
19
24
26
23
25
22
[Fuse Box Label, In Glove Box]
[Fuse Box, Front Left of Radiator]
LNW21ALF000401-X
27 28
No. Indication on label Capacity Devices connected
1 CONTROLLER 10A Control unit
2HAZARD,HORN (12V) 15A Hazard warning flashing lamp, horn
HAZARD,HORN (24V) 10A
3—10A—
4AIR CON (12V) 10A Air conditioner
HEATER,AIR CON (24V) 15A Heater, air conditioner
5 FUEL, SEAT HEATER (24V) 10A Fuel, seat heater
6 ABS, HAB, RETARDER (24V) 15A ABS, HAB, retarder
7 ROOM LAMP 15A Room lamp
8 STOP LAMP 10A Stop lamp

Engine Control System 1A-17
External Fuse Box
9 POWER WINDOW (24V) 20A Power window
10 TAIL.ILLUMI (12V) 15A Tail lamp
TAIL.ILUMI (24V) 10A
11 FOG.CORNER 10A Fog lamp, cornering lamp
12 ELEC.PTO (24V) 10A PTO switch (electric PTO)
13 WIPER,WASHER 15A Wiper, window washer
14 TURN 10A Turn signal lamp
15 GENERATOR (12V) 15A Generator
ELEC.PTO (24V) 20A PTO solenoid valve (electric PTO)
16 MIRROR HEAT (12V) 10A Heated side mirror
ENG.CONT (24V) 15A ECM
17 MIRROR 10A Electrically operated mirror
18 CIGAR,AUDIO 10A Cigarette lighter, audio
19 METER (12V) 10A Meter
METER (24V) 15A
20 ENGINE STOP (12V) 10A Engine stop
HSA (24V) 10A HSA
21 AIR BAG 10A SRS airbag
22 STARTER 10A Starter
23 H/LAMP RH 10A Headlamp, RH
24 H/LAMP LH 10A Headlamp, LH
25 HEATER (12V) 30A Heater
ENG CONTROLLER (24V) 30A ECM (except for turbocharged vehicles)
26 POWER WINDOW (12V) 30A Power window
No. Indication on label Capacity Devices connected
27 MARKER LAMP 10A Marker lamp
28 COND FAN 10A Condenser fan
No. Indication on label Capacity Devices connected

1A-18 Engine Control System
Relay Layout
LNW21ALF006101-X
Fuse &
Relay Box
Relay Box No.1
Relay Box No.2
RightFront
Upper
Spare Power Circuit
Cooler Relay
Bracket
1
19 20
2
3
4
17
5678910 11 12
13
14
15
16
18
No. Legend
112 V: On relay
24 V: Charge relay
2 Horn relay
312 V: ABS, VSV, FICD, EXH brake, valve (12 V)
24 V: Headlamp relay
4Tailrelay
512 V: Headlamp relay
24 V: 4WD relay
6 Dimmer relay
7 Power window relay
8 Fog lamp relay