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