3.
Monitor "HO2S(B2S1)" parameter on scantool
Specification : 0.1 ~ 0.9V
In order to control emissions of the CO, HC and NOx 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.
Checking output signals from HO2S under detecting condition, if an output signal within the detecting condition lasts continuously, PCM sets P2197. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item | Detecting Condition | Possible cause |
DTC Strategy | ● Determines if O2 sensor indicates lean exhaust while in Power Enrichment | ● Poor Connection ● Faulty HO2S ● Faulty PCM |
EnableConditions | ● Sensor not in cooled status ● Not in Transient Conditions status ● Airflow present ≥ 2 g/s ● Ignition voltage ≥ 10V ● Fuel reduction not active ● Engine running ● Engine running long enough ≥ 60sec. ● Power Enrichment conditions present ● Engine coolant warm enough ≥ 60℃( 140 °F) ● Above conditions met long enough ≥ 1.5sec. | |
Threshold value | ● O2 sensor voltage 〈 0.54V and, Air Fuel Ratio ≤ 13.5 | |
DiagnosisTime | ● Contineous (More than 11.25sec. failure for every 12.5sec. Test) | |
MIL On Condition | ● 2 Driving Cycles |
After warming-up, if accelerator pedal is released suddenly around 4000rpm, 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, HO2S signal will switch from lean to rich normally.
A/F Ratio | Output Voltage(V) |
Rich | 0.75 ~ 1.00V |
Lean | 0 ~ 0.12V |
Connect scantool to DLC(Data Link Connector)
Warm up the engine to normal operating temperature.
Monitor "HO2S(B2S1)" parameter on scantool
Specification : 0.1 ~ 0.9V
Does the "HO2S(B2S1)" parameter operates correctly ?
▶Fault is intermittent caused by poor contact in Sensor’s and/or PCM’s connector or was repairedand PCM memory was not cleared. Thoroughly check connectors for looseness, poorconnection, bending, corrosion, contamination, deterioration, or damage. Repair or replaceas necessary and go to "Verification of Vehicle Repair" procedure
▶Go to "Component Inspection" procedure.
Visual Inspection
Visually check HO2S as follow.
Contamination, deformation or age of HO2S(B2/S1)
Is the HO2S(B2/S1) normal ?
▶ Go to "Check performance of HO2S" as follows.
▶ Substitute with a known-good HO2S(B2S1) and check for proper operation. If the problem is corrected,replace HO2S(B2S1) and then go to "Verification of Vehicle Repair" procedure.
Check performance of HO2S
Connect scantool to DLC(Data Link Connector)
Warm up the engine to normal operating temperature.
Monitor signal waveform of HO2S with scantool.
Specification : 0.1 ~ 0.9V.
Is the HO2S(B2S1) working properly ?
▶ Substitute with a known-good PCM and check for proper operation. If the problem is corrected,replace PCM and then go to "Verification of Vehicle Repair" procedure.
There is a memory reset function on scantool that can erase optional parts automaticallydetected and memorized by PCM.
▶ Substitute with a known-good HO2S(B2S1) and check for proper operation. If the problem is corrected,replace HO2S(B2S1) and then go to "Verification of Vehicle Repair" procedure.
After a repair, it is essential to verify that the fault has been corrected.
Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
Using a Scantool, Clear the DTCs
Operate the vehicle within conditions noted in the freeze frame data or enable conditions
Monitor that all rediness test have been verified as " Complete "
Are any DTCs present ?
▶ Go to the applicable troubleshoooting procedure.
▶ System is performing to specification at this time.
