Isuzu 4HK-1, Manual, Page: 4 / 50

4
Isuzu 4HK-1 and 6HK-1 Engine Overview
The electronic control system for the Isuzu 4HK-1 and 6HK-1 Engines use input
information from a number of sensors and from the Excavator controller to determine
the quantity and timing of the fuel delivery to the engine.
The engine control module (ECM), is located on the inside rear of the cab. The ECM
has two connectors, one an 81 pin and one 40 pin, for inputs and outputs. The engine
control module requires downloading of control software to give it the ability to control all
functions.
Inputs to 40 pin engine harness connector:
•
The common rail fuel pressure sensor has 3 wires and is located on the common
rail. This sensor detects the fuel pressure in the common rail, converts the pressure
into a voltage signal, and sends the signal to the ECM. Higher common rail
pressure provides higher fuel pressure sensor voltage while lower pressure provides
lower fuel pressure sensor voltage.
•
The 2 wire variable resistor fuel temperature sensor is installed on the fuel supply
pump. The fuel temperature sensor measures the temperature of the drain fuel from
the pump. When the fuel temperature sensor is cold, the sensor resistance is high.
When the fuel temperature increases, the sensor resistance decreases. With high
sensor resistance, the ECM detects a high voltage on the signal circuit. With lower
sensor resistance, the ECM detects a lower voltage on the signal circuit.
Fuel Temp.
(
°
C)
Fuel Temp.
(
°
F)
Ohms
Ω
Fuel Temp.
(
°
C)
Fuel
Temp. (
°
F)
Ohms
Ω
140 284 75 40 104 1,150
120 248 111 20 68 2,450
100 212 184 0 32 5,740
80 176 318 -20 -4 15,000
60 140 584 -40 -40 45,770
•
The 2 wire engine coolant temperature sensor is located on the thermostat housing
at the right front corner of the engine. The coolant sensor's temperature detection
component uses a thermistor. A 5 volt reference voltage is applied at all times to the
sensor from the ECM. The ECM detects a voltage change due to a resistance value
change in the sensor caused by the coolant temperature change.
Coolant
Temp. (
°
C)
Coolant
Temp. (
°
F)
Ohms
Ω
Coolant
Temp. (
°
C)
Coolant
Temp. (
°
F)
Ohms
Ω
140 284 76 40 104 1,161
120 248 118 20 68 2,500
100 212 190 0 32 5,773
80 176 325 -20 -4 15,216
60 140 591 -40 -40 47,365