FI SYSTEM 4-49
“C44” HO2 SENSOR (HO2S) CIRCUIT MALFUNCTION
INSPECTION
• Remove the engine under cover and seat. (#3-3 and 6-4)
DETECTED CONDITION POSSIBLE CAUSE
Output voltage of HO
2
Sensor higher than the spec-
ification or lower than the specification.
• HO
2
sensor or its circuit open or short.
• Fuel system malfunction.
• ECM malfunction.
1
Turn the ignition switch OFF.
Check the HO
2 sensor coupler for loose or poor contacts.
If OK, then check the continuity.
Disconnect the HO
2 sensor coupler and ECM coupler.
Check the continuity between the HO
2 sensor coupler
terminal (White/Green) and ECM coupler terminal (White/
Green).
Also, check the infinity between the HO
2 sensor coupler
terminal and ground.
No
Ye s
Loose or poor contacts on the
ECM coupler.
Open or short circuit in the
White/Green wire.
No
Replace the HO
2 sensor with
a new one.
2
Connect the HO
2 sensor coupler and ECM coupler.
Insert the copper wires to the HO
2
sensor lead wire coupler.
Start the engine and warm up the engine up to engine
coolant temperature is 80 ˚C (176 ˚F).
Measure the HO
2 sensor output voltage at the coupler
(between White/Green and Black/Brown wires) when idling
condition.
Also, measure the HO
2 sensor output voltage while holding
the engine speed at 5 000 r/min.
1
2
ECM coupler
Ground
HO
2S
coupler
]
W/G
V
z
09900-25008: Multi circuit tester
[
Tester knob indication: Continuity (
]
)
;
HO
2 sensor output voltage at idle speed:
less than 0.4 V (
+
W/G –
-
B/Br)
HO
2 sensor output voltage at 5 000 r/min:
more than 0.6 V (
+
W/G –
-
B/Br)
z
09900-25008: Multi circuit tester
u
Tester knob indication: Voltage (
-
)
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