Component Location
Description
1. General Description
The HO2S is used to supply the ECM with information regarding the composition of the air/fuel mixture. The HO2S is positioned in the exhaust pipe ahead of the TWC. To measure the oxygen content, the HO2S requires a supply of ambient air as a reference. Since this is supplied through the wiring, the lead must not be clamped or damaged in any other way. The HO2S produces a voltage that varies between 0.1V and 0.9V under normal operating conditions. The Engine Control Module (ECM) monitors this voltage and determines if the exhaust gas is lean or rich. If the voltage input at the ECM is under approx. 0.45V the exhaust is lean, and if the voltage input is over approx. 0.45V the exhaust is rich. The ECM constantly monitors the HO2S signal during closed loop operation and compensates for a rich or lean condition by decreasing or increasing injector pulse width as necessary.
2. DTC Description
If the ECM detects no signal changes in Heated Oxygen Sensor, DTC P0134 is set.
DTC Detecting Condition
Item | Detecting Condition | Possible cause |
Monitoring Strategy | ? Signal check, wiring interruption | - Open HO2S - Short HO2S - Faulty HO2S - Faulty ECM - Poor connections between HO2S and ECM - Misplaced,bent,loose or corroded terminals. |
Threshold value | ? Signal output upstream O2 sensor : > 0.2V ? Signal output downstream O2 sensor : > 0.2V |
? Signal output upstream O2 sensor : < 0.4V , > 0.6V |
? Intemal resistance : > 20000? ?Exhaust gas temp. : > 600?(1112?) |
Enable Conditions | ? Volteg : > 10.7V ? Target lambda : = 1.0 ? Exhaust gas temp. : > 600?(1112?) , < 800?(1472?) ? Heating power : > 0.8 ? Dew point end etected downstream O2 ? sensor readiness time elapse : > 0.8s ? Time elapse after fuel cut-off : > 3.0s |
? Volteg : > 10.7V ? Target lambda : = 1.0 ? Exhaust gas temp. : > 600?(1112?) , < 800?(1472?) ? Heating power : > 0.8 ? Dew point end etected downstream O2 ? sensor readiness time elapse : > 0.8s ? Time elapse after fuel cut-off : > 3.0s |
? Volteg : > 10.7V ? Target lambda : = 1.0 ? Exhaust gas temp. : > 600?(1112?) , < 800?(1472?) ? Heating power : > 0.8 ? Dew point end etected downstream O2 ? sensor readiness time elapse : > 0.8s |
Diagnostic Time | ? > 1.3V |
? > 0.5V |
|
MIL on condition | |
Specification
For front HO2S |
When decelerating suddeniy from 4000rpm : 200mV or less |
When engine is suddenly raced : 600~1000mV |
1500rpm : The fluctuation between 400mV or less and 600~1000mV |
For Rear HO2S |
Part load(Approx. 2000rpm) : 500~1000mV |
Waveform Inspection in Oscilloscope Mode
This inspection procedure is recommended when service data with scan tool is not enough.
Warm up engine to normal operating temperature
Probe(+) : O2 sensor harness connector NO2.
Probe(-) : Chassis ground.
Specification
For front HO2S |
When decelerating suddeniy from 4000rpm : 200mV or less |
When engine is suddenly raced : 600~1000mV |
1500rpm : The fluctuation between 400mV or less and 600~1000mV |
For Rear HO2S |
Part load(Approx. 2000rpm) : 500~1000mV |
Signal Waveform
This figures show the waveform measured at terminal 2 of HO2S at idle RPM.
The average voltage of HO2S should be 0.5 V.
When sudden decceleration,the voltage at point ? should be below 0.2V.
The switching time marked ? from lean to rich should be within 200ms,if longer than 200ms HO2S may be not good.
The switching time marked ? from rich to lean should be within 300ms,if longer than 300ms HO2S may be not good.
In case the average voltage of HO2S is over 0.6V.
Possible cause:Injector leakage,faulty Pressure regurator Faulty MAPS, ECTS. |
The rear oxygen sensor output is usually not changeable like front oxygen sensor,however,if it moves like front oxygen sensor,the catalytic converter is broken.
Is Sensor Switching Properly
In case there is no symptom and wrong data but DTC is shown |
The problem may be intermittent so slightly shake the connector and harness vertically and horizontally to check if there is any data changes |
If the data changes normally, the problem was intermittent so erase DTC and verify the same DTC reoccure. Go to "Terminal and Connector inspection" procedure. |
In case there is symptom and wrong data with DTC |
Check open,short or connector’s connection for HO2S. |
Check the deterioration of HO2S performance. Go to "Circuit Inspection" procedure. |
Signal Waveform
This figures show the waveform measured at terminal 2 of HO2S at idle RPM.
The average voltage of HO2S should be 0.5 V.
When sudden decceleration,the voltage at point ? should be below 0.2V.
The switching time marked ? from lean to rich should be within 200ms,if longer than 200ms HO2S may be not good.
The switching time marked ? from rich to lean should be within 300ms,if longer than 300ms HO2S may be not good.
In case the average voltage of HO2S is over 0.6V.
Possible cause:Injector leakage,faulty Pressure regurator Faulty MAPS, ECTS. |
The rear oxygen sensor output is usually not changeable like front oxygen sensor,however,if it moves like front oxygen sensor,the catalytic converter is broken.