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In addition, the ECU also checks for an open circuit
in the HO2S output line.
Malfunction; out-of-range
a. WTS: Normal.
b. HO2S signal voltage has continued to be 0.1V or
lower for 3 min. or more after the staring sequence
was completed.
c. Water Temperature is higher than 80°C (176°F).
d. Engine speed is higher than 1,200 r/min.
e. Engine load is 25% or more. Judgment Criteria
f. Input voltage supplied to the ECU interface circuit is
4.5V or more when 5V is applied to HO2S output line
via a resistor.
Proper Operation
a. WTS: Normal.
b. Water Temperature is 50°C (122°F) or more.
c. Engine speed is between 1,500 and 3,000 r/min or
1,100 and 3,000 r/min.
d. Engine load is 25 - 60%.
e. Intake air temperature is -10°C (14°F) or more.
f. Under the closed loop air-fuel control.
g. Monitoring Time: 8sec.
TROUBLESHOOTING GUIDE
DTC detection condition
Failure Criteria
a. When the air-fuel ratio is forcibly changed (lean to
rich and rich to lean), the HO2S signal doesn't
provide response within 1.28 sec.
b. Monitored only once per trip.
CIRCUIT DIAGRAM
Probable cause
a. HO2S deteriorated
b. Open circuit in HO2S
output line
c. ECU failed
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