3.
Monitor "HO2S(B1/S1) Heater" 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.
If the PCM detects heater current is lower than threshold value for 2.5 seconds or over while enable condition is met PCM determines that a fault exists and a DTC is stored.
Item | Detecting Condition | Possible cause | |||||
DTC Strategy | ● Compares the current that is passing through the O2 Heater to a low limit | ● Poor Connection ● Contact Resistance ● HO2S(B1/S1) ● PCM | |||||
Enable Conditions | ● Engine Running 〉60sec. ● Heater Duty Cycle 〉0.4% ● Max. Duty Cycle - Min. Duty Cycle〈 0.05% ● Adove conditions are met 〉5sec. | ||||||
Threshold value | ● Filtered O2 Heater Current 〈 threshold value | ||||||
Diagnosis Time | ● Continuous (More than 2.5 second failure for every 5 second test ) | ||||||
MIL On Condition | ● 2 Driving Cycles | ||||||
The HO2S requires a minimum temperature to provide a closed loop fuel control system. So the HO2S contains a heater element to reduce its warm-up time and ensure its performance during all driving conditions. The PCM controls this heater element by duty cycle. The main relay supplies voltage to the heater and the PCM provides a ground circuit for activating the heater.
Condition | Current(A) | ||||||
Heater Current at 13.5V, 450℃(842°F) Exhaust | 0.52 ± 0.1 | ||||||
Heater In-rush Current at 21℃(69.8°F), 13.5V | 1.7 MAX | ||||||
Heater In-rush Current at -40℃(-40°F), 13.5V | 2.2 MAX | ||||||
IG "OFF" ＆ connect scantool.
ENG "ON" and warm -up the engine to normal operating temperature.
Monitor "HO2S(B1/S1) Heater" status on the service data.
Is the "HO2S Heater(B1/S1)" 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 " Component Inspection " procedure.
Check HO2S(B1/S1) Heater resistance
IG "OFF" and disconnect HO2S(B1/S1) connector
Measure resistance between terminal 1 and 2 of HO2S(B1/S1)(Component Side)
Heater | |||||||
Resistance (Ω) | 9.6 ± 1.5 at 21℃(69.8℉) | ||||||
Is the measured resistance within specification ?
▶ 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.
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
▶ 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.
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.
