1A
DTC P0031 / P0032: HO2S Heater Control Circuit Low / High (Sensor-1)
Wiring Diagram
1. Shield wire 4. “IG” fuse 7. To HO2S-2 heater 10. Relay box
2. Ignition switch 5. HO2S-1 8. ECM 11. “IGN1” fuse
3. Circuit fuse box 6. Heater 9. To other sensor    
DTC Detecting Condition and Trouble Area
DTC detecting condition Trouble area
Current of HO2S-1 heater is more than specified value or lower than specified value for 5 seconds continuously.
(2 driving cycle detection logic)
HO2S-1 heater circuit
HO2S-1 heater
ECM
DTC Confirmation Procedure
1) With ignition switch turned OFF, connect scan tool.
2) Turn ON ignition switch and clear DTC using scan tool.
3) Start engine and warm up to normal operating temperature.
4) Run engine at idle speed for 1 min. or more.
5) Check DTC and pending DTC.
DTC Troubleshooting
Step Action YES NO
1
Was “Engine and Emission Control System Check” performed?
Go to Step 2.
2
HO2S-1 heater power circuit check
1) Disconnect connector from HO2S-1 with ignition switch turned OFF.
2) Check for proper connection to HO2S-1 at “BLK/WHT” and “PNK/BLK” wire terminals.
3) If wire and connection are OK, measure voltage between “BLK/WHT” wire terminal and engine ground with ignition switch turned ON.
Is voltage over 10 V?
Go to Step 3.
“BLK/WHT” wire is open circuit or shorted to ground circuit.
3
HO2S-1 heater power circuit check
1) Disconnect connectors from ECM with ignition switch turned OFF.
2) Measure resistance between “BLK/WHT” wire terminal of HO2S-1 connector and “E118-28” terminal of ECM connector.
Is resistance below 5 Ω?
Go to Step 4.
“BLK/WHT” wire high resistance circuit.
4
HO2S-1 heater drive circuit check
1) Measure resistance between “E117-4” terminal of ECM connector and vehicle body ground.
Is resistance infinity?
Go to Step 5.
“PNK/BLK” wire shorted to ground circuit.
5
HO2S-1 heater drive circuit check
1) Turn ON ignition switch.
2) Measure voltage between “E117-4” terminal of ECM connector and vehicle body ground.
Is voltage 0 V?
Go to Step 6.
“PNK/BLK” wire shorted to power circuit.
6
HO2S-1 heater drive circuit check
1) Connect connector to HO2S-1 with ignition switch turned OFF.
2) Turn ON ignition switch.
3) Measure voltage between “E117-4” terminal of ECM connector and vehicle body ground with disconnect connector from ECM.
Is voltage over 10 V?
Go to Step 7.
“PNK/BLK” wire open circuit.
7
HO2S-1 heater check
1) Disconnect HO2S-1 coupler with ignition switch turned OFF.
2) Check HO2S-1 heater resistance referring to Heated Oxygen Sensor (HO2S-1 and HO2S-2) Heater On-Vehicle Inspection:M13A .
Is resistance within specified value?
Go to Step 8.
Replace HO2S-1.
8
HO2S-1 heater power circuit check
1) Connect connector to HO2S-1 with ignition switch turned OFF.
2) Measure resistance between “E118-28” and “E117-4” terminals of ECM connector.
Is resistance below 12 Ω?
HO2S-1 heater circuit are OK.
Substitute a known-good ECM and recheck.
“BLK/WHT”, “PNK/BLK” and/or “BLK” wire high resistance circuit.
NOTE:
Upon completion of inspection and repair work, perform “DTC Confirmation Procedure” and confirm that the trouble has been corrected.