In order to control emissions of the CO, HC and NOx components of the exhaust gas, heated oxygen sensor (HO2S), mounted on the front side and rear side of catalytic converter, detects the oxygen content in the exhaust gas. The front HO2S signal is used to control air/fuel ratio (closed loop fuel control) and the rear HO2S signal is used to monitor front HO2S and catalyst for proper operation. The HO2S requires a minimum temperature to operate properly and provide a closed loop fuel control system. The HO2S contains the heater element to reduce its warming-up time and ensure its performance during all driving conditions. The oxygen sensor generates a voltage that indicates the difference between the oxygen content of the exhaust stream and the oxygen content of ambient air. When the exhaust stream is “rich,” there is more oxygen in the ambient air than in the exhaust stream, so the voltage will be higher.
DTC DESCRIPTION
Checking output signals from HO2S under detecting condition, if PCM judges it's signals too slow, PCM sets P0133. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
DTC DETECTING CONDITION
Item
Detecting Condition
Possible cause
DTC Strategy
●
Monitor HO2S's response rate
●
Poor connection
●
Faulty HO2S
●
Faulty PCM
Enable Conditions
●
Engine warm-up sufficiently
●
Engine run time ＞ 60sec
●
Drive at a steady speed between 45-55 mph(72-88 km/h)
●
Engine Coolant ＞ 70℃( 158 °F)
●
No disabling faults
Threshold value
●
The calculated response rate is too slow (out of threshold in PCM)
Diagnosis Time
●
Continuous
MIL On Condition
●
2 Driving Cycles
SIGNAL WAVEFORM AND DATA
After warming-up, if accelerator pedal is released suddenly around 4000rpm, the HO2S signal reading will be lower than 200mV resulting from Fuel cut-off for the moment. Conversely, if suddenly accelerator pedal is depressed, HO2S signal reading will be around 0.6V ~1.0V. At idle, Normally HO2S signal will switch from lean to rich with 3 Hz. And as racing, Its frequency rises.
SPECIFICATION
(Reference only)
Test Condition
HO2S Voltage(Sensor1)
HO2S Voltage(Sensor2)
HO2S Signal
at idle after warm-up
Signal is commonly switching from rich to lean more than 3 times in 10 sec.
Signal is commonly above 0.6V.
HO2S signal at open circuit
(Pumping current OFF)
Approx. 0.45V
HO2S signal at open circuit
(Pumping current ON)
Approx. 3.5V
SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1.
Check DTC Status
(1)
Connect scantool to Data Link Connector(DLC).
(2)
IG "ON".
(3)
Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F4(DTAL) to check DTC's information from the DTCs menu
(4)
Read "DTC Status" parameter.
(5)
Is parameter displayed "Present fault"?
▶ Go to "Component Inspection" procedure.
▶ Clear DTC and check if this DTC is set after test-driving under enable conditions. If DTC isn't displayed after the test, it was intermittent fault. Go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1.
Replace the HO2S.
2.
Clear DTC with scantool.
3.
Start the engine and warm it up until the radiator fan comes on( more than at least 10 minutes).
4.
Drive at a steady speed between 45-55 mph(72-88 km/h) for 120 sec.
5.
Stop and then maintain idle state.
6.
Check if O2 sensor monitoring readiness is complete.
7.
Does the scan tool show DTC P0133?
▶ Substitute with a known - good PCM and check for proper operation.
If the problem is corrected, go to "Verification of Vehicle Repair" procedure.
▶ Troubleshooting is finished.
VERIFICATION OF VEHICLE REPAIR
After a repair, it is essential to verify that the fault has been corrected.
1.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode
2.
Press F4(DTAL) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3.
Read "DTC Status" parameter
4.
Is parameter displayed "History(Not Present) fault"?
▶ System performing to specification at this time. Clear the DTC.
