1A-109 Engine General Information and Diagnosis:
2 1) Connect the HO2 sensor coupler.
2) Insert the needle pointed probes to the lead wire coupler.
3) Turn the ignition switch ON and measure the heater
voltage between the W/B wire and ground.
If the tester voltage indicates the battery voltage, it is
good condition.
NOTE
Battery voltage can be detected only before
starting the engine.
Special tool
(A): 09900–25008 (Multi-circuit tester set)
(B): 09900–25009 (Needle pointed probe set)
Tester knob indication
Voltage ( )
HO2 sensor heater voltage
Battery voltage
((+) terminal: W/B – (–) terminal: Ground)
Is the voltage OK?
• O/W or W/B wire
open or shorted to
the ground, or poor
“40” connection.
• Recheck each
terminal and wire
harness for open
circuit and poor
connection.
• If wire and
connection are OK,
intermittent trouble or
faulty ECM.
• Replace the ECM
with a known good
one, and inspect it
again. Refer to “ECM
Removal and
Installation in Section
1C (Page 1C-1)”.
• Open or short circuit
in the W/B wire or O/
W wire.
• Loose or poor
contacts on the ECM
coupler or HO2
sensor coupler.
Step Action Yes No
(A)
(B)
I718H1110232-02
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