The rear heated oxygen sensor is mounted on the rear side of the Catalytic Converter (warm-up catalytic converter) or in the rear exhaust pipe, which is able to detect catalyst efficiency. The rear heated oxygen sensor (HO2S) produces a voltage between 0V and 1V. This rear heated oxygen sensor is used to estimate the oxygen storage capability. If a catalyst has good conversion properties, the oxygen fluctuations are smoothed by the oxygen storage capacity of the catalyst. If the conversion provided by the catalyst is low due to aging, poisoning or misfiring, then the oxygen fluctuations are similar to signals from the front oxygen sensor.
DTC DESCRIPTION
The ECM monitors rich-lean switching time of rear heated oxygen sensor (HO2S) after fuel cut-off to validate dynamic behavior of rear heated oxygen sensor (HO2S). After detection of fuel cut-off engine operating state, the ECM measures rich-lean switching time of the rear heated oxygen sensor (HO2S) signal and compares it to the predetermined limit value. DTC P0139 is set when the switching time is bigger than the limit value.
DTC DETECTING CONDITION
Item
Detecting Condition
Possible Cause
DTC Strategy
●
Slow response(Switching time check at entry in fuel cut off)
●
Leak in intake or exhaust system
●
Faulty fuel system.
●
Front and rear HO2S connections reversed.
●
Contact resistance in connectors
●
HO2S contamination
Enable Conditions
●
Coolant temp ＞74.25℃(165.65℉)
●
Sensor preheating and full phase finished
●
Catalyst temp.model ＞348℃(658.4℉)
●
No relevant failure
●
11V＜ Battery voltage ＜16V
●
Downstream O2 sensor signal at entry in fuel cut off ＞ 0.55V
●
O2 Sensor operative readiness detected
Threshold Value
●
Average ratio(between measured and maximum allowed switching time at entry in fuel cut-off) ＞ 1
Diagnostic Time
●
5 fuel cut-off phases
MIL On Condition
●
2 Driving Cycles
SIGNAL WAVEFORM AND DATA
Test Condition
Scan Tool Parameter
O2 SNSR VOL.-B1/S1
O2 SNSR VOL.-B1/S2
Normal Value when circuit is normal
Idle after warm up
Signal is switching from rich(above 0.45V) to lean(below 0.45V) a minimum of 3 times in 10 seconds.
above 0.7V
HO2S(B1S1) signal circuit open
Approx. 0.43~0.45V
-
HO2S(B1S2) signal circuit open
-
Approx. 0.43~0.45V
SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
2.
Press F4(DTAL) to select DTC information from the DTCs menu.
3.
Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.
4.
Read "DTC Status" parameter.
5.
Is parameter displayed "History(Not Present) fault"?
note
-
History (Not Present) fault : DTC occurred but has been cleared.
-
Present fault : DTC is occurring at present time.
▶ Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
▶ Go to next step as below.
EXHAUST SYSTEM INSPECTION
1.
Check the exhaust system for an exhaust leak near the engine.
2.
Was an exhaust leak found?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to next step as below
AIR LEAKAGE INSPECTION
1.
Visually/physically inspect the following items:
A.
Vacuum hoses for splits, kinks and improper connections.
B.
Exhaust system between HO2S and Three way catalyst for air leakage
C.
EVAP system for leakage
D.
PCV hose for proper installation
2.
Was a problem found in any of the above areas?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to next step as below
VISUAL/PHYSICAL INSPECTION
1.
Visually/physically inspect the following items:
A.
Check for corrosion on terminals
B.
Check for terminal tension ( at the HO2S and at the ECM)
C.
Check for damaged wiring
D.
Check the HO2S ground circuit for a good connection
E.
Check front and rear HO2S for connections being reversed.
2.
Was a problem found in any of the above areas?
▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Go to next step as below
COMPONENT INSPECTION
1.
Visually/physically inspect the following conditions:
A.
Ensure that the sensor is securely installed
B.
Check for corrosion on terminals
C.
Check for damaged wiring
D.
Repair as necessary and go to next step
2.
Warm up the engine to normal operating temperature and let it idle.
3.
Connect Scantool and monitor the O2 SNSR VOL.-B1/S2 parameter on the Scantool data list.
Specification : Above 0.7V at idle
4.
Is sensor data near the specified value?
▶ Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection. Repair as necessary and go to "Verification of Vehicle Repair" procedure
▶ Check HO2S for contamination, deterioration, or damage. Substitute with a known-good HO2S and check for proper operation. If the problem is corrected, replace HO2S and then go to "Verification of Vehicle Repair" procedure
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
