The heated oxygen sensor (HO2S) monitor tracks the rate of voltage change during the rise and fall of the HO2S signal. When the rate of voltage change is less than a calibrated value, the PCM begins to modify the fuel trim attempting to increase the HO2S voltage switch rate. This DTC sets when the PCM is at the allowable limit or has exceeded an allowable length of time for fuel trim modification, without etecting an acceptable rate of voltage change.
Item | Detecting Condition | Possible Cause | |
Case 1 | DTC Strategy |
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Transient time monitor(Rich to Lean). * HMC Remark : Catalyst monitoring is done by Rich to Lean step only. | 1. Poor connection 2. HO2S(S2) 3. PCM |
Enable Conditions |
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B+ greater than 11.0 V.
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Engine speed greater than 1200rpm and less than 3520 rpm.
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EGT around downstream O2S greater than 425 ℃(797 °F).
•
Intergrated Exhaust gas mass flow greater than 0.2 kg/h.
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Exhaust gas mass flow greater than 10 kg/h.
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Delta Exhaust gas mass flow greater than -15 kg/h and less than 15 kg/h.
•
Fuel system status : Fuel cut off.
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Downstream O2S voltage before fuel cut greater than 0.63 V. | ||
Threshold Value |
•
Transient time(average) : Minimum duration(1/Max gradient) of downstream O2S voltage from 0.63V to 0.25V during fuel cut off greater than 0.30 sec(3 times per driving). | ||
Diagnostic Time |
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3 valid fuel cut-off phases. | ||
Case 2 | DTC Strategy |
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Response time monitor (Rich to Lean) error will be stored immediately when exceeding the threshold once(3times monitoring). | |
Enable Conditions |
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B+ greater than 11.0 V.
•
Engine speed greater than 1200 rpm and less than 3520 rpm.
•
EGT around downstream O2S greater than 425 ℃(797 °F).
•
Intergrated Exhaust gas mass flow greater than 0.2 kg/h.
•
Exhaust gas mass flow greater than 10 kg/h.
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Delta Exhaust gas mass flow greater than -15 kg/h and less than 15 kg/h.
•
Fuel system status : Fuel cut off.
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Downstream O2S voltage before fuel cut greater than 0.63 V. | ||
Threshold Value |
•
Response time OSC integration of catalyst When downstream O2S voltage from 0.63V to 0.25V during fuel cut off greater than Exh.gas mass flow. | ||
Diagnostic Time |
•
3 valid fuel cut-off phases. | ||
Item | Detecting Condition | Possible Cause | |
Case 3 | DTC Strategy |
•
Transient time monitor(Lean to Rich). | 1. Poor connection 2. HO2S(S2) 3. PCM |
Enable Conditions |
•
B+ greater than 11.0 V.
•
Engine speed greater than 1200 rpm and less than 3520 rpm.
•
EGT around downstream O2S greater than 425 ℃.
•
Intergrated Exhaust gas mass flow greater than 0.2 kg/h.
•
Exhaust gas mass flow greater than 8 kg/h.
•
Delta Exhaust gas mass flow greater than -30 kg/h and less than 50 kg/h.
•
Fuel system status : after a fuel cut off.
•
Downstream O2S voltage before fuel cut greater than 0.15 V. | ||
Threshold Value |
•
Transient time(average) : Minimum duration(1/Max gradient) of downstream O2S voltage from 0.25V to 0.63V after fuel cut in greater than 0.45 sec(3 times per driving). | ||
Diagnostic Time |
•
3 valid oxygen purge phases after fuel cut-off. | ||
Case 4 | DTC Strategy |
•
Response time monitor (Lean to Rich) error will be stored immediately when exceeding the threshold once(3times monitoring). | |
Enable Conditions |
•
B+ greater than 11.0 V.
•
Engine speed greater than 1200 rpm and less than 3520 rpm.
•
EGT around downstream O2S greater than 425 ℃(797 °F).
•
Intergrated Exhaust gas mass flow greater than 0.2 kg/h.
•
Exhaust gas mass flow greater than 8 kg/h.
•
Delta Exhaust gas mass flow greater than -30 kg/h and less than 50 kg/h.
•
Fuel system status : after a fuel cut off.
•
Downstream O2S voltage before fuel cut greater than 0.15 V. | ||
Threshold Value |
•
Response time OSC integration of catalyst When downstream O2S voltage from 0.25V to 0.63V after fuel cut in greater than Exh.gas mass flow. | ||
Diagnostic Time |
•
3 valid oxygen purge phases after fuel cut-off. | ||
MIL ON Condition |
•
2 Driving Cycles. | ||
※ S1 : upstream oxygen sensor / S2 : downstream oxygen sensor
