Isuzu Trooper (1998-2002 year). Manual — part 644

6E–224

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

5. Push the terminal and the connector to engage the

locking tangs.

070

6. Close the secondary locking hinge.

Com-Pack III

General Information

The Com-Pack III terminal looks similar to some
Weather-Pack terminals. This terminal is not sealed and
is used where resistance to the environment is not
required. Use the standard method when repairing a
terminal. Do not use the Weather-Pack terminal tool
5-8840-0388-0 or equivalent. These will damage the
terminals.

Metri-Pack

Tools Required

5-8840-0632-0 Terminal Remover

Removal Procedure

Some connectors use terminals called Metri-Pack Series
150. These may be used at the engine coolant
temperature (ECT) sensor.

1. Slide the seal (1) back on the wire.

2. Insert the 5-8840-0632-0 tool or equivalent (3) in

order to release the terminal locking tang (2).

060

3. Push the wire and the terminal out through the

connector. If you reuse the terminal, reshape the
locking tang.

Installation Procedure

Metri-Pack terminals are also referred to as “pull-to-seat”
terminals.

1. In order to install a terminal on a wire, the wire must be

inserted through the seal (2) and through the
connector (3).

2. The terminal (1) is then crimped onto the wire.

061

3. Then the terminal is pulled back into the connector to

seat it in place.

6E–225

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

General Description

(ECM and Sensors)

57X Reference ECM Input

The engine control module (ECM) uses this signal from
the crankshaft position (CKP) sensor to calculate engine
RPM and crankshaft position at all engine speeds. The
ECM also uses the pulses on this circuit to initiate injector
pulses. If the ECM receives no pulses on this circuit, DTC
P0337 will set. The engine will not start and run without
using the 57X reference signal.

A/C Request Signal

This signal tells the ECM when the A/C mode is selected
at the A/C control head.
Refer to

A/C Clutch Circuit Diagnosis for A/C wiring

diagrams and diagnosis for the A/C electrical system.

Crankshaft Position (CKP) Sensor

The crankshaft position (CKP) sensor provides a signal
used by the engine control module (ECM) to calculate the
ignition sequence. The CKP sensor initiates the 57X
reference pulses which the ECM uses to calculate RPM
and crankshaft position.
Refer to

Electronic Ignition System for additional

information.

Camshaft Position (CMP) Sensor and
Signal

The camshaft position (CMP) sensor sends a CMP signal
to the ECM. The ECM uses this signal as a “cylinder
distinction” to trigger the injectors in the power order. If the
ECM detects an incorrect CMP signal while the engine is
running, DTC P0341 will set, and the ECM triggers the
injectors in the power order.
Refer to

DTC P0341.

Engine Coolant Temperature (ECT) Sensor

The engine coolant temperature (ECT) sensor is a
thermistor (a resistor which changes value based on
temperature) mounted in the engine coolant stream. Low
coolant temperature produces a high resistance of
100,000 ohms at –40

°

C (–40

°

F). High temperature

causes a low resistance of 70 ohms at 130

°

C (266

°

F).

The ECM supplies a 5-volt signal to the ECT sensor
through resistors in the ECM and measures the voltage.
The signal voltage will be high when the engine is cold and
low when the engine is hot. By measuring the voltage, the
ECM calculates the engine coolant temperature. Engine
coolant temperature affects most of the systems that the
ECM controls.
The Tech 2 displays engine coolant temperature in
degrees. After engine start-up, the temperature should
rise steadily to about 85

°

C (185

°

F). It then stabilizes

when the thermostat opens. If the engine has not been
run for several hours (overnight), the engine coolant

temperature and intake air temperature displays should
be close to each other. A hard fault in the engine coolant
sensor circuit will set DTC P0117 or DTC P0118.

0016

Electrically Erasable Programmable Read
Only Memory (EEPROM)

The electrically erasable programmable read only
memory (EEPROM) is a permanent memory chip that is
physically soldered within the ECM. The EEPROM
contains the program and the calibration information that
the ECM needs to control powertrain operation.
Unlike the PROM used in past applications, the EEPROM
is not replaceable. If the ECM is replaced, the new ECM
will need to be programmed. Equipment containing the
correct program and calibration for the vehicle is required
to program the ECM.

Intake Air Temperature (IAT) Sensor

The intake air temperature (IAT) sensor is a thermistor
which changes its resistance based on the temperature of
air entering the engine. Low temperature produces a high
resistance of 100,000 ohms at –40

°

C (–40

°

F). High

temperature causes low resistance of 70 ohms at 130

°

C

(266

°

F) . The ECM supplies a 5-volt signal to the sensor

through a resistor in the ECM and monitors the signal
voltage. The voltage will be high when the incoming air is
cold. The voltage will be low when the incoming air is hot.
By measuring the voltage, the ECM calculates the
incoming air temperature.
The Tech 2 displays the temperature of the air entering
the engine. The temperature should read close to the
ambient air temperature when the engine is cold and rise
as underhood temperature increases. If the engine has
not been run for several hours (overnight), the IAT sensor
temperature and engine coolant temperature should read
close to each other. A fault in the IAT sensor circuit will set
DTC P0112 or DTC P0113.

6E–226

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

0018

Manifold Absolute Pressure (MAP) Sensor

The manifold absolute pressure (MAP) sensor responds
to changes in intake manifold pressure. The MAP sensor
signal voltage to the ECM varies from below 2 volts at idle
(high vacuum) to above 4 volts.
The MAP sensor is used to determine the following:

D

Boost pressure for injector control.

D

Barometric pressure (BARO).

If the ECM detects a voltage that is lower than the
possible range of the MAP sensor, DTC P0107 will be set.
A signal voltage higher than the possible range of the
sensor will set DTC P0108. An intermittent low or high
voltage will set DTC P1107 or DTC P1106, respectively.
The ECM can detect a shifted MAP sensor. The ECM
compares the MAP sensor signal to a calculated MAP
based on throttle position and various engine load factors.
If the ECM detects a MAP signal that varies excessively
above or below the calculated value, DTC P0106 will set.

Engine Control Module (ECM)

The engine control module (ECM) is located in the engine
room.
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. It can recognize
operational problems, alert the driver through the MIL
(Service Engine Soon lamp), and store diagnostic trouble
codes (DTCs). DTCs identify the problem areas to aid the
technician in making repairs.

ECM Function

The ECM supplies 5, 12 and 110 volts to power various
sensors or switches. The power is supplied through
resistances in the ECM which are so high in value that a
test light will not light when connected to the circuit. In
some cases, even an ordinary shop voltmeter will not give
an accurate reading because its resistance is too low.
Therefore, a digital voltmeter with at least 10 megohms
input impedance is required to ensure accurate voltage
readings. The ECM controls output circuits such as the

injectors, glow relays, etc., by controlling the ground or
the power feed circuit through transistors or through
either of the following two devices:

D

Output Driver Module (ODM)

D

Quad Driver Module (QDM)

ECM Components

The ECM is designed to maintain exhaust emission levels
to government mandated standards while providing
excellent driveability and fuel efficiency. The ECM
monitors numerous engine and vehicle functions via
electronic sensors such as the crankshaft position (CKP)
sensor, and vehicle speed sensor (VSS). The ECM also
controls certain engine operations through the following:

D

Fuel injector control

D

Rail pressure control

ECM Voltage Description

The ECM supplies a buffered voltage to various switches
and sensors. It can do this because resistance in the
ECM is so high in value that a test light 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-megohm
input impedance digital voltmeter to assure accurate
voltage readings.
The input/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.” These switches are arranged in
groups of 4 and 7, called either a surface-mounted quad
driver module (QDM), which can independently control up
to 4 output terminals, or QDMs which can independently
control up to 7 outputs. Not all outputs are always used.

ECM Input/Outputs

Inputs – Operating Conditions Read

D

Air Conditioning “ON” or “OFF”

D

Engine Coolant Temperature

D

Crankshaft Position

D

Electronic Ignition

D

Manifold Absolute Pressure

D

Battery Voltage

D

Intake Throttle Position

D

Vehicle Speed

D

Fuel Temperature

D

Oil Temperature

D

Intake Air Temperature

D

EGR boost pressure

D

Oil rail pressure

D

Camshaft Position

D

Accelerator position

Outputs – Systems Controlled

D

Exhaust Gas Recirculation (EGR)

D

Injector Control

D

QWS

6E–227

4JX1–TC ENGINE DRIVEABILITY AND EMISSIONS

D

QOS

D

Diagnostics

–

Malfunction Indicator Lamp (Service Engine
Soon lamp)

–

Data Link Connector (DLC)

–

Data Output

ECM Service Precautions

The 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’s circuits unless
instructed to do so. These circuits should only be tested
using digital voltmeter. The ECM should remain
connected to the ECM or to a recommended breakout
box.

Intake Throttle Position (ITP) Sensor

ITP sensor is a potentiometer type and installed to the
intake throttle valve body. A voltage of 5V is applied
constantly from ECM to ITP sensor thereby to determine
by change in voltage the opening of the intake throttle
valve during warming up.

Transmission Range Switch

IMPORTANT:

The vehicle should not be driven with the

transmission range switch disconnected; idle quality will
be affected.
The four inputs from the transmission range switch
indicate to the ECM which position is selected by the
transmission selector lever.
For more information on the transmission on the
transmission range switch, refer to

Automatic

Transmission.

Accelerator Position Sensor (AP)

AP sensor is a potentiometer type and installed to
accelerator pedal bracket. A voltage of 5V constantly
applied from ECM to the sensor thereby to determine the
accelerator pedaling angle by change in voltage. Further,
this sensor is provided with an accelerator switch, which
is set off only when the accelerator pedal is stepped on.

Aftermarket Electrical and Vacuum
Equipment

Aftermarket (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 it leaves the factory. No allowances have been
made in the vehicle design for this type of equipment.

NOTE: No add-on vacuum equipment should be added
to this vehicle.

NOTE: 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 radios. Therefore, the first step
in diagnosing any powertrain problem is to eliminate all
aftermarket electrical equipment from the vehicle. After
this is done, if the problem still exists, it may be diagnosed
in the normal manner.

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. Less than 100 volts of static
electricity can cause damage to some electronic
components. By comparison, it takes as much as 4000
volts for a person to feel even the zap of a static
discharge.

TS23793

There are several ways for a person to become statically
charged. The most common methods of charging are by
friction and induction.

D

An example of charging by friction is a person sliding
across a vehicle seat.

D

Charge by induction occurs when a person with well
insulated shoes stands near a highly charged object
and momentary touches ground. Charges of the
same polarity are drained off leaving the person
highly charged with the opposite polarity. Static
charges can cause damage, therefore it is important
to use care when handling and testing electronic
components.

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

D

Do not touch the ECM connector pins or soldered
components on the ECM circuit board.

D

Do not open the replacement part package until the
part is ready to be installed.

D

Before removing the part from the package, ground
the package to a known good ground on the vehicle.

D

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.