Isuzu N-Series. Manual - part 733

6E-354    Engine Control System (4HK1) 

Idle Up Sensor Replacement

Removal Procedure

1. Turn off the ignition.
2. Remove the idle up sensor knob (1).
3. Disconnect the idle up sensor connector.
4. Remove the idle up sensor holder (2).

5. Remove the idle up sensor (3).

Installation Procedure

1. Install the idle up sensor (3).
2. Install the idle up sensor holder (2).
3. Install the idle up sensor knob (1).
4. Connect the idle up sensor connector.

Intake Air Temperature (IAT) Sensor
Replacement

Removal Procedure

1. Turn off the ignition.
2. Disconnect the intake air temperature (IAT) sensor

connector (1).

3. Remove the IAT sensor.

Installation Procedure

1. Coat threads of the IAT sensor with sealer

(9985490) in full circumference.

2. Tighten the IAT sensor.

Tighten:
IAT sensor to 10.8 — 16.3 N

⋅m (1.1 — 1.7 kg⋅m /

8.0 — 12.0 lb

⋅ft)

3. Connect the IAT sensor connector.

Vehicle Speed Sensor (VSS) Replacement

Removal procedure

1. Turn off the ignition.
2. Disconnect the vehicle speed sensor connector

(1).

3. Remove the vehicle speed sensor (2).

N6A6584E

1

N6A6559E

 Engine Control System (4HK1)    6E-355

Installation procedure

1. Tighten the vehicle speed sensor (2).

Tighten:
Vehicle speed sensor to 27 N

⋅m (2.8 kg⋅m / 20 lb⋅ft)

2. Connect the vehicle speed sensor connector (1).

N6A6560E

6E-356    Engine Control System (4HK1) 

Description and Operation

Engine Control Module (ECM) Description

Engine Control Module (ECM) Service Precautions

Important:
Symbol warns you of an electric shock hazard. To avoid
shock and possible serious injury, DO NOT touch the
terminals. When disconnecting the harness
connectors, always turn OFF the ignition switch or
disconnect the battery cable.

The engine control module (ECM) is designed to
withstand normal current draws associated with vehicle
operation. Avoid overloading any circuit. When testing
for opens and shorts, do not ground or apply voltage to
any of the ECM circuits unless instructed to do so. In
some cases, these circuits should only be tested using
a digital multimeter (DMM). The ECM should remain
connected to the ECM harness.

The engine control module (ECM) is located inside of
engine side cover on the left via mounting bracket and
is beside the engine. The ECM mainly controls the
following:

• The fuel system control
• The exhaust gas recirculation (EGR) system

control

• The preheating (glow) system control
• On-board diagnostics for engine control

The ECM constantly observes the information from
various sensors. The ECM controls the systems that
affect vehicle performance. The ECM performs the
diagnostic function of the system. The ECM can
recognize operational problems, alert the driver
through the malfunction indicator lamp (MIL), and store
diagnostic trouble codes (DTCs). DTCs identify the
system faults to aid the technician in making repairs.

ECM Voltage Description
The ECM supplies a buffered voltage to various
switches and sensors. The ECM can do this because
resistance in the ECM is so high in value that a test
lamp may not illuminate when connected to the circuit.
An ordinary shop voltmeter may not give an accurate
reading because the voltmeter input impedance is too
low. Use a 10-megaohm input impedance DMM, to
ensure accurate voltage readings. The input and/or
output devices in the ECM include analog-to-digital
converters, signal buffers, counters, and special
drivers. The ECM controls most components with
electronic switches which complete a ground circuit
when turned ON.

Aftermarket Electrical and Vacuum Equipment
Aftermarket or add-on electrical and vacuum
equipment is defined as any equipment which connects
to the vehicle’s electrical or vacuum systems that is
installed on a vehicle after the vehicle leaves the
factory. No allowances have been made in the vehicle
design for this type of equipment. No add-on vacuum
equipment should be added to this vehicle. Add-on
electrical equipment must only be connected to the
vehicle’s electrical system at the battery power and
ground. Add-on electrical equipment, even when
installed to these guidelines, may still cause the
powertrain system to malfunction. This may also
include equipment not connected to the vehicle
electrical system such as portable telephones and
audios. Therefore, the first step in diagnosing any
powertrain fault is to eliminate all aftermarket electrical
equipment from the vehicle. After this is done, if the
fault still exists, the fault may be diagnosed in the
normal manner.

CAUTION

To avoid electric shock;
Set the key switch to the "OFF" or "LOCK"
position before checking or repairing the
computer, wiring or/and connectors.

N6A6480E

CAUTION

To avoid electric shock;
Set the key switch to the "OFF" or "LOCK"
position before checking or repairing the
computer, wiring or/and connectors.

N6A6481E

 Engine Control System (4HK1)    6E-357

Electrostatic Discharge Damage
Electronic components used in the ECM are often
designed to carry very low voltage. Electronic
components are susceptible to damage caused by
electrostatic discharge. By comparison, as much as
4,000 volts may be needed for a person to feel even
the zap of a static discharge. There are several ways
for a person to become statically charged. The most
common methods of charging are by friction and
induction.

• An example of charging by friction is a person

sliding across a vehicle seat.

Important:
To prevent possible electrostatic discharge damage,
follow these guidelines:

• Do not touch the ECM connector pins or soldered

components on the ECM circuit board.

• Do not open the replacement part package until

the part is ready to be installed.

• Before removing the part from the package,

ground the package to a known good ground on
the vehicle.

• If the part has been handled while sliding across

the seat, while sitting down from a standing
position, or while walking a distance, touch a
known good ground before installing the part.

• Charge by induction occurs when a person with

well insulated shoes stands near a highly charged
object and momentarily touches ground. Charges
of the same polarity are drained off leaving the
person highly charged with opposite polarity.

Malfunction Indicator Lamp (MIL) Operation
The malfunction indicator lamp (MIL) is located in the
instrument panel cluster. The MIL will display the
following symbols when commanded ON:

The MIL indicates that an emission or performance
related fault has occurred and vehicle service is
required. The following is a list of the modes of
operation for the MIL:

• The MIL illuminates for approximately 3 seconds

when the ignition switch is turned ON, with the
engine OFF. This is a bulb test to ensure the MIL is
able to illuminate. (Without speed limiter device)

• The MIL illuminates for approximately 15 seconds

and blinks 3 times when the ignition switch is
turned ON, with the engine OFF. This is a bulb test
to ensure the MIL is able to illuminate and a speed
limiter device installation check. (With speed limiter
device)

• The MIL remains illuminated if the engine control

module (ECM) detects a fault. A diagnostic trouble
code (DTC) is stored any time the ECM illuminates
the MIL due to an emission or performance related
fault.

N6A6482E

N6A6483E

Without speed limiter device

With speed limiter device

ON

OFF

1 sec. 1 sec. 1 sec.

15 sec.

1 sec. 1 sec. 1 sec.

Ignition switch ON

ON

OFF

Ignition switch ON

3 sec.