Ho2S Inspection - TOHATSU BFT75A Service Manual

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FUEL SYSTEM

HO2S INSPECTION

SYSTEM INSPECTION
1. HO2S operation test 1
Turn the combination switch OFF and disconnect
the HO2S 4P connector.
Connect the battery positive (+) cable to the sensor
side No.4 (White) terminal and the battery negative
cable (–) to the sensor side No.3 (White) terminal of
the HO2S 4P connector respectively.
Start the engine and let it run at 3,000 min
3 minutes or more under no load.
Snap the engine throttle with the engine speed in
the range between idle speed and 4,000 ± 500 min
(rpm).
Let the engine idle for 1 minute or more.
Make sure that the voltage is above 0.6 V at the
No.1 (Black) terminal and No.2 (Gray) terminal of
the HO2S sensor side 4P connector.
If the voltage is temporarily below 0.6 V, recheck the
above inspection after the engine idles for 1 minute
or more.
The normal voltage at idle speed is above 0.6 V.
•
Depending on the condition of the warm-up, the
voltage may become temporarily less than 0.6 V.
Is the voltage above 0.6 V?
YES
NO
2. HO2S operation test 2
Snap the engine throttle with the engine speed in
the range between idle speed and 4,000 ± 500 min
(rpm).
Or let it run at 4,000 ± 500 min
and then quickly close the throttle valve.
Is the measurement above 0.6 V when the
throttle is fully open and below 0.6 V when the
throttle is fully closed?
YES
NO
HEATER INSPECTION
Turn the combination switch OFF and disconnect the
HO2S 4P connector.
Measure the resistance between the No.3 (White) and
No.4 (White) terminals of the HO2S sensor.
Resistance:11.7 - 15.6 Ω
If the resistance is not as specified, replace the HO2S.
5-108
– GO TO STEP 2.
– Faulty HO2S.
-1 (rpm) under no load,
– HO2S is normal.
– Faulty HO2S.
HO2S 4P CONNECTOR SENSOR SIDE
O2
-1 (rpm) for
(Black)
-1
O2HT
(White)
-1
HO2S 4P CONNECTOR
SENSOR SIDE
O2HT
(White)
SG
(Gray)
(White)
12V BATTERY
IGP3
(White)