Engine General Information and Diagnosis: 1A-68
8
HO2S heater relay circuit check
1) Measure wire resistance between coil ground terminal of
relay connector and vehicle body ground.
Is measured resistance lower than 1
Ω
?
Output wire of relay
connector is open or
short to ground.
Repair or replace
defective circuit.
9
A/F sensor heater check
1) Check heater resistance of A/F sensor referring to “Air
Fuel Ratio (A/F) Sensor On-Vehicle Inspection: in
Section 1C”.
Is A/F sensor heater in good condition?
Go to Step 10.
Replace A/F sensor.
10
A/F sensor heater control circuit check
1) Disconnect connector from ECM with ignition switch
turned OFF.
2) Check for proper connection of A/F sensor heater circuit
terminal to ECM connector.
3) If connection are OK, measure each wire resistance of
sensor heater control circuit at ECM connector between
ECM to A/F sensor and ECM to vehicle body ground.
Is each measured wire resistance lower than 1
Ω
?
Go to Step 11.
Repair or replace
defective wire circuit.
11
A/F sensor heater circuit check
1) Measure insulation resistance between control terminal
of A/F sensor heater and ground terminal of A/F sensor
heater at ECM connector.
Is measured resistance infinity?
Substitute a known
good ECM and recheck.
Repair or replace short
wire.
Step
Action
Yes
No
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