Doosan G643E - Specification

G643(E) Service Manual Chapter 5. Engine Management System (EMS) 187
Signal Wave Form
The amplitude of the signal output of the rear HO2S
is small compared to the front HO2S because the
rear HO2S detects emission gas purified by the
catalytic converter. This illustration is the normal
signal waveform of the rear HO2S at idle.
Specification
Temperature Temperature
(℃) (℉)
Rear
HO2S
Heater
Resis-
tance(Ω)
(℃) (℉)
Rear
HO2S
Heater
Resistanc
e(Ω)
20 68 9.2 400 752 17.7
10 212 10.7 500 932 19.2
200 392 13.1 600 1,112 20.7
300 572 14..6 700 1,272 22.5
ECT (Engine Coolant Temperature)
Sensor [G643E and G643]
Component Location
ECT Senser
Description
The Engine Coolant Temperature Sensor (ECTS) is
located in the engine coolant passage of the cylinder
head for detecting the engine coolant temperature.
The ECTS uses a thermister whose resistance
changes with the temperature. The electrical
resistance of the ECTS decreases as the
temperature increases, and increases as the
temperature decreases. The reference 5 V in the
ECM is supplied to the ECTS via a resistor in the
ECM. That is, the resistor in the ECM and the
thermistor in the ECTS are connected in series.
When the resistance value of the thermistor in the
ECTS changes according to the engine coolant
temperature, the output voltage also changes.
Sensor Inspection
1. Remove the engine coolant temperature sensor
from the intake intake manifold.
2. With the temperature sensing portion of the
engine coolant temperature sensor immersed in
hot water, check resistance.
Temperature ℃ (℉) ECTS Resistance(kΩ)
20(68) 2.31~2.59
3. If the resistance deviates from the standard value
greatly, replace the sensor.