Doosan G20P-5, Service Manual, Page: 171 / 306

G424F(FE) Service Manual Chapter 5. Engine Management System (EMS) 169
Oxygen Sensor (Post-Catalyst)
Component Location
Description
The rear heated oxygen sensor is mounted on the
rear side of the Catalytic Muffler, which detects the
catalyst efficiency. The rear heated oxygen sensor
(HO2S) produces a voltage between 0V and 1V.
This rear heated oxygen sensor is used to estimate
the oxygen storage capability. If a catalyst has good
conversion properties, the oxygen fluctuations are
smoothed by the oxygen storage capacity of the
catalyst. If the conversion provided by the catalyst is
low due to aging, poisoning or misfiring, then the
oxygen fluctuations are similar to signals from the
front oxygen sensor.
Schematic Diagram
[CIRCUIT DIAGRAM]
[HARNESS CONNECTORS]
C22
ECM
HO2S (B1/S2)
After Main Relay
3
4
2
1
B19 - HO2S SIGNAL
B1 - HO2S GND
A23 - HO2S HEATER
(B1/S2)
1 2
3 4
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