Engine General Information and Diagnosis: 1A-93
2 HO2S-1 output voltage check
1) Connect scan tool to DLC with ignition switch turned
OFF.
2) Warm up engine to normal operating temperature and
keep it at 2000 r/min. for 60 sec.
3) Repeat racing engine (Repeat depressing accelerator
pedal 5 to 6 times continuously to enrich A/F mixture and
take foot off from pedal to enlean it) and check HO2S
output voltages displayed on scan tool.
Is over 0.6 V and below 0.3 V indicated?
Intermittent trouble.
Check for intermittent
referring to “Intermittent
and Poor Connection
Inspection in Section
00”. If check result is
OK, go to Step 3.
Go to Step 3.
3 HO2S-1 ground check
1) Disconnect connector from HO2S-1 with ignition switch
turned OFF.
2) Check for proper connection to HO2S-1 at “BLK/RED”,
“WHT”, “BLK/WHT” and “YEL” wire terminals.
3) If wire and connection are OK, measure resistance
between “YEL” wire terminal of HO2S-1 connector and
engine ground.
Is resistance less than 5
Ω
?
Go to Step 4. “YEL” wire is open or
high resistance circuit.
Poor “C37-57” terminal
connection. Faulty ECM
ground.
If they are OK,
substitute a known-
good ECM and recheck.
4 Wire circuit check
1) Turn OFF ignition switch.
2) Remove ECM from its bracket with ECM connectors
connected.
3) Measure resistance between “WHT” wire terminal of
HO2S-1 connector and “C37-10” terminal of ECM
connector.
Is resistance less than 5
Ω
?
Go to Step 5. “WHT” wire is high
resistance circuit or
open circuit. Poor “C37-
10” terminal connection
of ECM connector.
Faulty ECM ground. If
they are OK, substitute
a known-good ECM and
recheck.
5 Wire circuit check
1) Disconnect connectors from ECM with ignition switch
turned OFF.
2) Measure resistance between “WHT” wire terminal of
HO2S-1 connector and vehicle body ground.
Is resistance infinity?
Go to Step 6. “WHT” wire is shorted to
ground circuit.
6 HO2S-1 heater circuit check
1) Check HO2S-1 heater circuit referring to “DTC P0031 /
P0032: HO2S Heater Control Circuit Low / High
(Sensor-1)”.
Is it in good condition?
Go to Step 7. Repair HO2S-1 circuit.
7 Exhaust system check
1) Check exhaust system for exhaust gas leakage.
Is it OK?
Go to Step 4 in “DTC
P0171 / P0172: Fuel
System Too Lean /
Rich”.
If it is in good condition,
go to Step 8.
Repair leakage of
exhaust system.
8 Air intake system check
1) Check air intake system for clog or leak.
Is it OK?
Check HO2S-1 referring
to “HO2S-1 and HO2S-
2 Heater On-Vehicle
Inspection in Section
1C”.
If it is in good condition,
substitute a known-
good ECM and recheck.
Repair or replace air
intake system.
Step Action Yes No
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