3.
Monitor "HO2S(B1/S1)" status on the service data.
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 every 15 sec. under detecting condition, if an output signal is below 0.04V for more than 12.5 sec., PCM sets P0131. MIL(Malfunction Indication Lamp) turns on when the malfunction lasts till consecutive 2 driving cycle.
Item | Detecting Condition | Possible cause | |||||
DTC Strategy | ● Signal low | ● Poor Connection ● Short to ground in harness ● HO2S(B1/S1) ● PCM | |||||
Enable Conditions | ● Battery voltage ≥ 10V ● The minimum airflow ≥ 2g/s ● Engine running state ≥ 60sec. ● The coolant temperature ≥ 60℃(140℉) ● The feed-back control (the closed loop) state ● No fuel-cut state ● Above conditions are met 〉5 sec. ● HO2S heated state ● No transient condition | ||||||
Threshold value | ● The voltage of HO2S(B1/S1)〈 0.04V | ||||||
Diagnosis Time | ● Continuous (more than 12.5 sec. failure for every 15 sec.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.
Air/fuel mixture | Voltage(V) | ||
Rich | 0.75 ~ 1V | ||
Lean | 0 ~ 0.12V |
※In case of open circuit, voltage is set to 0.45V(Pumping current OFF) or 3.5V(Pumping current ON)
IG "OFF" ＆ connect scantool.
ENG "ON" and warm -up the engine to normal operating temperature.
Monitor "HO2S(B1/S1)" status on the service data.
Is the service data displayed correctly ?
▶ Fault is intermittent caused by poor contact in the sensor’s and/or PCM’s connector or was repaired and PCM 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 "Signal Circuit Inspection" procedure.
IG "OFF" and disconnect HO2S(B1/S1) connector.
IG "ON" and ENG "OFF"
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
Is the measured voltage within specification?
▶ Go to "Component Inspection" procedure.
▶ Repair short to ground in harness, and go to "Verification of Vehicle Repair" procedure.
Check HO2S(B1/S1)
IG "OFF" and disconnect HO2S(B1/S1) connector.
Check HO2S(B1/S1) for damage or contamination caused by a foreign substance.
Is the HO2S(B1/S1) normal?
▶ Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM 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
There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others
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.
