Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual - part 13

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–47

Mass Air Flow (MAF) Sensor & Intake Air
Temperature (IAT) Sensor

The mass air flow (MAF) sensor is part of the intake air
system.
It is fitted between the air cleaner and turbocharger and
measure the mass air flowing into the engine.
The mass air flow (MAF) sensor uses a hot film element
to determine the amount of air flowing into the engine.
The mass air flow (MAF) sensor assembly consist of a
mass air flow (MAF) sensor element and an intake air
temperature sensor that are both exposed to the air flow
to be measured.
The mass air flow (MAF) sensor element measures the
partial air mass through a measurement duct on the
sensor housing.
Using calibration, there is an extrapolation to the entire
mass air flow to the engine.

The IAT sensor is a thermistor. A temperature changes
the resistance value. And it changes voltage. In other
words it measures a temperature value. Low air
temperature produces a high resistance.

The ECM supplies 5 volts signal to the IAT sensor
through resisters in the ECM and measures the voltage.
The signal voltage will be high when the air temperature
is cold, and it will be low when the air temperature is hot.

Pedal/Throttle Position Sensor (TPS)

-30 -20 -10

100 110 120 130

Characteristic of IAT Sensor

Temperature (

Resistance ( )

(1) Throttle Position Sensor (TPS)
(2) Idle Switch

+5V

Output

Ground

+5V

Ground

6E–48

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

The TPS is a potentiometer connected to throttle shaft
on the throttle body. It is installed to the main TPS and
idle switch.
The engine control module (ECM) monitors the voltage
on the signal line and calculates throttle position. As the
throttle valve angle is changed when accelerator pedal
moved. The TPS signal also changed at a moved
throttle valve. As the throttle valve opens, the output
increases so that the output voltage should be high.
The engine control module (ECM) calculates fuel
delivery based on throttle valve angle.

Crankshaft Position (CKP) Sensor

The CKP sensor is located on top of the flywheel
housing of the flywheel and fixed with a bolt.
The CKP sensor is of the magnet coil type. The
inductive pickup sensors four gaps in the flywheel
exciter ring and is used to determine the engine speed
and engine cylinder top dead center (TDC).

Engine Coolant Temperature (ECT) Sensor

The ECT sensor is a thermistor. A temperature changes
the resistance value. And it changes voltage. In other
words it measures a temperature value. It is installed on
the coolant stream. Low coolant temperature produces
a high resistance.
The ECM supplies 5 volts signal to the ECT sensor
through resisters in the ECM and measures the voltage.
The signal voltage will be high when the engine
temperature is cold, and it will be low when the engine
temperature is hot.

Characteristic of TPS

Throttle Angle (%)

Output V

oltage

(V)

(1) Engine Coolant Temperature (ECT) Sensor
(2) Thermo Unit for Water Temperature Gauge

-30

-20

-10

100 110 120

Characteristic of ECT Sensor

Temperature (deg. C)

Resistance ( )

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

6E–49

Vehicle Speed Sensor (VSS)

The VSS is a magnet rotated by the transmission output
shaft. The VSS uses a hall element. It interacts with the
magnetic field treated by the rotating magnet. It outputs
pulse signal. The 12 volts operating supply from the
meter fuse.
The engine control module (ECM) calculates the vehicle
speed by VSS.

EGR EVRV (4JA1-TC Only)

The EGR system on this engine is largely responsible
for a reduction of the NOx exhaust emission.
The amount of EGR is controlled by EVRV (electrical
vacuum regulating valve) via the engine control module
(ECM) command signal depends on the engine speed,
operating of the accelerator pedal and engine coolant
temperature.
The EVRV is shaped to control vacuum applied to the
diaphragm chamber of the EGR valve based on duty
signal sent from the ECM.

(1) EGR EVRV
(2) Connecting to Vacuum Pump
(3) Connecting to EGR Valve

7.1ms

Time

0.7ms

age

Off duty 10% =EGR Pulse Ratio 10%

7.1ms

Time

Vol

tage

Off duty 70% =EGR Pulse Ratio 70%

6.4ms

6E–50

4JA1-TC/4JH1-TC ENGINE DRIVEABILITY AND EMISSIONS

GENERAL DESCRIPTION FOR INJECTION

PUMP

Outline

Instead of the previous face cam type, the radial plunger
distributor type injection pump utilizes a cam ring to
enable fuel injection at high-pressures, marking it
suitable for small, high-speed direct injection diesel
engines. This pump was developed to provide the most
suitable fuel injection quantity and injection timing to
satisfy the demand for engine reliability, driveability, low
smoke, low noise, high output and clear exhaust
emissions.

Characteristic of VP44 Injection System

1. High Pressure Injection

The radial plunger distributor type injection pump is
capable of generating pressure of 100 Mpa
(approximately 1000 Bar) demanded by small, high
speed direct injection diesel engines.

2. High Pressure Atomization of Fuel Injected from
the Nozzle

Through high pressure fuel injection, the fuel is
atomized at high pressure with a high penetrating force
(the fuel droplets penetrate further) and with greater

dispersion and distribution (mixing with air is improved)
and results in better combustion. This contributes to
cleaner emissions.

3. Optimum Fuel Injection

High speed control of fuel injection quantity and fuel
injection timing, is performed by the control unit,
enabling lower fuel cost and high output.

4. Improved Durability

The components used in the pump are very resistant to
high pressure, ensuring improved durability.

5. Improved Engine Matching

As fuel injection is controlled by cylinder selective
adaptation, smooth running is improved.

6. Improved Reliability

As a control unit system with both an engine control
module (ECM) and a pump control unit (PSG) is used,
the control system is extremely reliable.

7. Improved Power Performance

As the control unit controls the optimum fuel injection
quantify corresponding to accelerator position,
increased torque in low accelerator pedal positions is
possible, enabling improved power performance.

8. Decreased Smoke at Acceleration

When the amount of injected fuel is increased, to
increase engine power at acceleration, the excess fuel
usually generates smoke. The VP44 fuel injection pump,
accurately controls fuel injection quantity even in this
range to prevent the generation of smoke without
adversely affecting acceleration.

9. Additional Devices are Unnecessary

Such additional devices as the boost compensator and
the aneroid compensator are unnecessary, as the
control unit compensates, based on signals from each
sensor. This results in less “clutter” injection pump.

10. Self Diagnosis Function

The system includes a self-diagnosis function, which
displays error codes to facilitate the diagnosis of
malfunctions.

(1) Drive Shaft
(2) Feed Pump
(3) Pump Camshaft Speed Sensor
(4) Pump Control Unit (PSG)
(5) Distributor Head
(6) Constant Pressure Valve (CPV) Holder
(7) High Pressure Solenoid Valve
(8) Constant Pressure Valve (CPV)
(9) Timing Control Valve (TCV)

(10) Timer
(11) Radial Plunger High Pressure Pump

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