13117780-13117761-13117888-13117907-13117815-13117745-13117796-13117853-13117839-13117869

COMPONENT LOCATION

GENERAL DESCRIPTION

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

Due to possible oxygen sensor defects (e.g. reference air poisoning) or faults in the injection system (e.g. leaking fuel injector), the rear oxygen sensor may not provide the expected lean or rich signal level during fuel cut-off or full load condition. Hence, the oxygen sensor signal is checked for plausibility during this engine operating states.There are 2 cases which DTC P0140 sets.

Signal monitoring during fuel cut-off: The ECM monitors rear O2 sensor signal level during fuel cut-off which normally shows near 0V and sets DTC P0140 when signal level is too high.

Signal monitoring after fuel cut-off: The ECM monitors rear O2 sensor signal level after leaving fuel cut-off and sets DTC P0140 when signal remains at or below 0.6V.

DTC DETECTING CONDITION

Item		Detecting Condition	Possible Cause
DTC trategy	Case1)	● Voltage range check	● Related fuse blown or missing ● Contact resistance in connectors ● HO2S contamination
DTC trategy	Case2)	● Voltage range check
Enable Conditions	Case1)	● O2 sensor operative readiness detected ● Integrated mass air flow in lask fuel cut off ＞ 4g ● Integrated mass air flow in part load ＞ 250g ● Coolant temperature ＞ 74.25℃ ● Downstream O2 sensor signal at end of last fuel cut off ＜ 0.25V ● Sensor preheating and fuel heating phases finished ● Catalyst temperature ＞ 348℃ (658℉) ● No relevant failure ● 11V ＜ Battery voltage ＜ 16V
Enable Conditions	Case2)	● O2 sensor operative readiness detected ● 20 ＜ Integrated mass air flow in lask fuel cut off ＜ 360g ● Sensor preheating and fuel heating phases finished ● No relevant failure ● 10V ＜ Battery voltage ＜ 16V
Threshold Value	Case1)	● Voltage ＜ 0.55V
Threshold Value	Case2)	● Voltage with fuel cut ＞ 0.1V
Diagnostic Time	Case1)	● 3 vaild fuel cut-off phases
Diagnostic Time	Case2)	● 2 sec.
Mil On Condition		● 2 Driving Cycles

SIGNAL WAVEFORM AND DATA

Test Condition		Scan Tool Parameter
Test Condition		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

note

If any DTCs relating to HO2S are stored, do ALL REPAIRS associated with those codes before proceeding with further troubleshooting

Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.

Press F4(DTAL) to select DTC information from the DTCs menu.

Confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions.

Read "DTC Status" parameter.

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.

TERMINAL AND CONNECTOR INSPECTION

Ignition "ON" ＆ Engine "OFF"

Monitor the O2 SNSR VOL.-B1/S2 parameter on the Scantool data list while wiggling the wiring harness and related connectors.

The value should remain more or less unchanged. If not, check for the following conditions:

Check for corrosion on terminals

Check for terminal tension ( at the HO2S and at the ECM)

Check for damaged wiring

Check the HO2S ground circuit for a good connection

Check the 15A sensor2 fuse

Check front and rear HO2S for connections being reversed.

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 belowTerminal and Connector Inspection

COMPONENT INSPECTION

Visually/physically inspect the following conditions:

Ensure that the sensor is securely installed

Check for corrosion on terminals

Check for damaged wiring

Repair as necessary and go to next step

Warm up the engine to normal operating temperature and let it idle.

Connect Scantool and monitor the O2 SNSR VOL.-B1/S2 parameter on the Scantool data list.

Specification : Above 0.7V at idle

Is sensor switching properly?

▶ 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.

Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.

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.

Read "DTC Status" parameter.

Is parameter displayed "History(Not Present) fault"?

▶ System performing to specification at this time. Clear the DTC

▶ Go to the applicable troubleshooting procedure.