2008 Kia Sorento 3.3L Eng LX DTC P0131 HO2S CIRCUIT LOW VOLTAGE (BANK 1/SENSOR 1) COMPONENT LOCATION Fig 1: Identifying HO2S GENERAL DESCRIPTION In order to control emissions of the CO, HC and x 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 an output signal is below 0.04V for more than predetermined time, ECM sets P0131. MIL (Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle. DTC DETECTING CONDITION DTC DETECTING CONDITION Item Detecting Condition Possible cause DTC Strategy Monitor signal voltage Enable Conditions Threshold value Battery voltage 10V Engine running 60 sec. Engine warm up state The voltage of HO2S (B1/S1) < 0.04V Poor connection Short to ground in harness HO2S (B1/S1) ECM http://www2.prodemand.com/print/index?content=article&module=false&tab=false&terms=false 1/7
Diagnosis Time Continuous (more than 12.5 sec. failure for every 15 sec. test) MIL On Condition 2 Driving Cycles SPECIFICATION (REFERENCE ONLY) SPECIFICATION Test Condition HO2S Signal at idle after warmup HO2S signal at open circuit (Pumping current OFF) HO2S signal at open circuit (Pumping current ON) HO2S Voltage (Sensor1) Signal is normally switching from rich to lean more than 3 times in 10 sec. Approx. 0.45V Approx. 3.5V HO2S Voltage (Sensor2) Signal is normally above 0.6V. SCHEMATIC DIAGRAM http://www2.prodemand.com/print/index?content=article&module=false&tab=false&terms=false 2/7
Fig 2: HO2S Schematic Diagram SIGNAL WAVEFORM AND DATA http://www2.prodemand.com/print/index?content=article&module=false&tab=false&terms=false 3/7
Fig 3: Signal Waveform And Data After warming up, if accelerator pedal is released suddenly around 4000 RPM, 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. At higher engine RPM, the switching frequency increases. MONITOR DTC STATUS 1. Check DTC Status 1. Connect scan tool to Data Link Connector (DLC). 2. IG "ON". 3. Select "Diagnostic Trouble Codes (DTCs)" mode, and then Press F5 (INFO) to check DTC's information from the DTCs menu. 4. Read "DTC Status" parameter. Fig 4: Scan Tool Screen Display DTC Status 5. Is "Present" Fault displayed? 1. Go to "TERMINAL AND CONNECTOR INSPECTION " procedure. http://www2.prodemand.com/print/index?content=article&module=false&tab=false&terms=false 4/7
TERMINAL AND CONNECTOR INSPECTION 1. 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, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "VERIFICATION OF VEHICLE REPAIR " procedure. 1. Many malfunctions in the electrical system are caused by poor harness and terminal condition. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage. 2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. 3. Has a problem been found? SIGNAL CIRCUIT INSPECTION 1. Repair as necessary and go to "VERIFICATION OF VEHICLE REPAIR " procedure 1. Go to "SIGNAL CIRCUIT INSPECTION " procedure. 1. IG "OFF" and disconnect HO2S (B1/S1) connector. 2. IG "ON" and ENG "OFF" 3. Measure voltage between terminal 3 of HO2S (B1/S1) harness connector and chassis ground. Specification: Approx. 3.5V when pumping current is ON Approx. 0.45V when pumping current is OFF 4. Is the measured voltage within specification? COMPONENT INSPECTION 1. Go to "COMPONENT INSPECTION " procedure. 1. Repair short to ground in harness, and go to "VERIFICATION OF VEHICLE REPAIR " procedure. 1. Check the Signal waveform of HO2S 1. IG "OFF" and connect HO2S connector. 2. Engine start. 3. After warming up, monitor signal waveform of HO2S with scan tool. http://www2.prodemand.com/print/index?content=article&module=false&tab=false&terms=false 5/7
Fig 5: HO2S Signal Waveform Graph 4. Is the sensor switching properly? 2. Check HO2S 1. Go to step 2. 1. Substitute with a known good HO2S and check for proper operation. If the problem is corrected, go to "VERIFICATION OF VEHICLE REPAIR " procedure. 1. IG "OFF" and disconnect HO2S connector. 2. Check that the HO2S is securely installed. 3. Check the HO2S for contamination or damage 4. Is the sensor normal? 1. Substitute with a known good ECM and check for proper operation. If the problem is corrected, go to "VERIFICATION OF VEHICLE REPAIR " procedure. 1. Substitute with a known good HO2S and check for proper operation. If the problem is corrected, go to "VERIFICATION OF VEHICLE REPAIR " procedure. TE: There is a memory reset function on scan tool that can erase optional parts automatically detected and memorized by ECM. Before or after testing ECM on the vehicle, use this function before reusing the ECM VERIFICATION OF VEHICLE REPAIR After a repair, it is essential to verify that the fault has been corrected. http://www2.prodemand.com/print/index?content=article&module=false&tab=false&terms=false 6/7
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode 2. Press F5 (INFO) 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 "History (Not Present)" fault displayed? 1. System performing to specification at this time. Clear the DTC 1. Go to the applicable troubleshooting procedure. http://www2.prodemand.com/print/index?content=article&module=false&tab=false&terms=false 7/7