Isuzu KB P190. Manual — part 330

6E-286 Engine Control System (4JH1)

Exhaust Gas Recirculation (EGR) Solenoid Valve

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The engine control module (ECM) controls the exhaust

gas recirculation (EGR) flow amount based on the

engine speed, engine coolant temperature, intake air

temperature, barometric pressure and fuel injection

quantity. The ECM controls the EGR valve by

controlling the EGR solenoid valve. The mass air flow

(MAF) sensor monitors EGR gas flow amount. An

expected MAF amount should be detected while the

engine running.

Intake Air Temperature (IAT) Sensor

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The intake air temperature (IAT) sensor is fitted

between the air cleaner and turbocharger internal to the

mass air flow (MAF) sensor. The IAT sensor is a

variable resistor. The IAT sensor measures the

temperature of the air entering the engine. The engine

control module (ECM) supplies 5 volts to the IAT signal

circuit and a ground for the IAT low reference circuit.

When the IAT sensor is cold, the sensor resistance is

high. When the air temperature increases, the sensor

resistance decreases. With high sensor resistance, the

ECM detects a high voltage on the IAT signal circuit.

With lower sensor resistance, the ECM detects a lower

voltage on the IAT signal circuit.

Mass Air Flow (MAF) Sensor

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The mass air flow (MAF) sensor is an air flow meter that

measures the amount of air that enters the engine. It is

fitted between the air cleaner and turbocharger. A small

quantity of air that enters the engine indicates

deceleration or idle. A large quantity of air that enters

the engine indicates acceleration or a high load

condition. The MAF sensor assembly consists of a MAF

sensor element and an intake air temperature sensor

that are both exposed to the air flow to be measured.

The MAF sensor element measures the partial air mass

through a measurement duct on the sensor housing.

Engine Control System (4JH1) 6E-287

Vehide Speed Sensor (VSS)

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Legend

1. Vehicle Speed Sensor (VSS) 2WD with A/T

2. Vehicle Speed Sensor (VSS) except 2WD with

A/T

The vehicle speed sensor (VSS) is used by the engine

control module (ECM) and speedometer, which

generates a speed signal from the transmission output

shaft. The VSS uses a hall effect element. It interacts

with the magnetic field created by the rotating magnet

and outputs square wave pulse signal. The ECM

calculates the vehicle speed by the VSS.

The following waveform aids to diagnose when there is

an oscilloscope or equivalent.

- VSS waveform cycle shorten as the vehicle

speed increases.

Terminal: 68 (+) / GND (-)
Scale: 5V/div 50ms/div
Condition: Approximately 20km/h (12MPH)

0V

6E-288 Engine Control System (4JH1)

Fuel Injection System Description

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Legend

1. Drive

Shaft

2. Fuel Feed Pump

3. Pump Camshaft Position (CMP) Sensor

4. Fuel Injection Pump Control Unit (PCU)

5. Distributor

Head

6. Constant Pressure Valve (CPV) Holder

7. Fuel Injection Solenoid Valve

8. Constran Pressure Valve (CPV)

9. Timing Control Valve (TCV)

10. Timer

11. Radial Plunger

Bosch VP44 Fuel Injection Pump
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 low exhaust
emissions.
The engine control module (ECM) calculates the
desired fuel injection quantity and timing using data sent
from various sensor s. These desired data are sent to
the fuel injection pump control unit (PCU) via a
controller area network (CAN) communication bus. The
PCU also receives signals from the internal inputs:
pump camshaft position (CMP) sensor that is located
inside the fuel injection pump to determine the cam ring

rotation angle and the fuel injection pump speed. The
fuel temperature (FT) sensor is internal the PCU. These
values are used to compare the desired values sent
from the ECM then PCU determines the injection timer
piston position and fuel injection quantity, and actuates
timing control valve (TCV) & fuel injection solenoid
valve based on control maps in the PCU.

The timing device changes the optimum injection
timing against various engine conditions. The
pressure of the fuel fed from the feed pump is
adjusted and it acts to the timing plunger by TCV
controlled fuel pressure.

(The TCV is installed to the

fuel injection pump rear side and it is controlled by duty
ratio cycle from the PCU.)

The timing plunger is

connected to the cam ring by a ball pin. Axial
movement of the timing plunger is transferred to the
cam ring in the form of rotational movement.

Engine Control System (4JH1) 6E-289

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Legend

1. Drive

Shaft

2. Feed

Pump

3. Pump Camshaft Position (CMP) Sensor

4. Fuel Injection Pump Control Unit (PCU)

5. Distributor

Head

6. Constant Pressure Valve (CPV) Holder

7. Fuel Injection Solenoid Valve

8. Constant Pressure Valve (CPV)

9. Timing Control Valve (TCV)

10. Timer

11. Radial Plunger

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Legend

1. Rotor

Shaft

2. Radial

Plunger

3. High Pressure Passage

4. Low Pressure Inlet

5. Distribution

Slit

6. Valve

Needle

7. Barrel

8. Annular

Passage

9. Fuel

Return

10. Fuel Injection Solenoid Valve

11. High Pressure Outlet

12. Diaphragm Chamber

13. Accumulator Diaphragm