3.
Monitor "HO2S(B1S1)" parameter on scantool.
The heated oxygen sensors are mounted on the front side and the rear sied of Catalytic Converter (warm-up catalytic converter), which detects the oxygen concentration 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 heated oxygen snesor (HO2S) produces a voltage that varies between 0V and 1V. When the air/fuel ratio is lean, the oxygen concentration in the exhaust gas increases and the front HO2S outputs a low voltage (approximately 0 ~ 0.1 V).When the air/fuel ratio is rich, the oxygen concentration in the exhaust gas decreases and the front HO2S output a high voltage (approximately 0.8 ~ 1 V). The ECM constantly monitors the HO2S and increases or decreases the fuel injection duration by using the HO2S signal, which is called closed-loop fuel control operation.
If ECM detects that the internal resistance of heater is out of threshold value, ECM sets DTC P0135.
Item | Detecting Condition | Possible Cause |
DTC Strategy | ● Check heating condition | ● Poor connection ● Open or short to ground in control circuit ● B1S1 ● ECM |
Enable Conditions | ● Exhaust gas temperature (model) 450∼530 ℃ ● Battery voltage 10.7∼15.6 V | |
Threshold Value | ● Internal resistance 〉 threshold f(exh. temp., heater power) | |
Diagnostic Time | ||
MIL ON Condition | ● 3 driving cycle |
※ B1S1 : upstream oxygen sensor / B1S2 : downstream oxygen sensor
ITEM | Specification |
Heater Resistance | Approx. 9.0Ω (20℃) |
Connect scantool to DLC (Data Link Cable).
Warm up the engine to normal operating temperature.
Monitor "HO2S(B1S1)" parameter on scantool.
Is the "HO2S(B1S1)" parameter displayed correctly?
▶ 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.
▶ Go to "Terminal and Connector Inspection" procedure.
Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.
Has a problem been found?
▶ Repair as necessary and go to "Verification of vehicle Repair" procedure.
▶ Go to " Power Circuit Inspection " procedure.
IG "OFF".
Disconnect HO2S(B1S1) connector.
IG "ON" ＆ ENG "OFF".
Measure voltage between terminal 3 of HO2S (B1S1) harness connector and chassis ground.
Specification : B+
Is the measured voltage within specification?
▶ Go to "Control Circuit Inspection" procedure.
▶ Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedure.
IG "OFF".
Disconnect HO2S(B1S1) connector.
IG "ON" ＆ ENG "OFF"
Measure voltage between terminal 4 of HO2S(B1S1) harness connector and chassis ground.
Specification : Approx. 3.5V
Is the measured voltage within specification?
▶ Go to "Component Inspection" procedure.
▶ Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedure.
Check Heater resistance.
IG "OFF".
Disconnect HO2S(B1S1) connector.
Measure resistance bwteen terminal 3 and 4 of HO2S(B1S1) connector.(Component Side)
ITEM | Specification |
Heater Resistance | Approx. 9.0Ω (20℃) |
Is the measured resistance within specification ?
▶ Substitute with a known - good ECM and check for proper operation.
▶ If the problem is corrected, replace ECM and go to "Verification of Vehicle Repair" procedure.
▶ Substitute with a known - good HO2S(B1/S1) and check for proper operation.
▶ If the problem is corrected, replace HO2S(B1/S1) and go to "Verification of Vehicle Repair" procedure.
After a repair, it is essential to verify that the fault has been corrected.
Connect scan tool and select "Diagnostic Trouble Codes(DTCs)" mode.
Clear the DTCs and Operate the vehicle within DTC Enable conditions in General information.
Are any DTCs present ?
▶ Go to the applicable troubleshooting procedure.
▶ System is performing to specification at this time.
