P0139

DTC P0139 - O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2)

1. OUTLINE OF DIAGNOSIS
Detect the slow response of rear oxygen sensor.

- Diagnostic Method
Measure the response time of the output change of the rear oxygen sensor when the A/F ratio changes from rich to lean. And Judge NG when the measured response time is larger than the threshold value.




2. COMPONENT DESCRIPTION




3. ENABLE CONDITION

4. GENERAL DRIVING CYCLE
Perform the diagnosis only once when fuel shut-off in deceleration after rapid acceleration. (Pay attention to oxygen sensor voltage for the timing of deceleration in order to calculated the diagnostic value.)

5. DIAGNOSTIC METHOD




When the oxygen sensor output voltage changes 0.55 V (rich) to 0.25 V (lean), calculate the Min. value of response time regarded as judgment value while the output varies from 0.5 V to 0.3 V.




- Abnormality Judgment
1. Judge NG when the judgment value is larger than the threshold value after fuel cut at deceleration.
Response time (Diagnosis value) greater than Threshold value -> Abnormal

NOTE: Variation time of rear oxygen sensor output voltages is short during fuel cut at deceleration. Carry out the NG judgment only after the fuel cut at deceleration. As for OK judgment, without the condition of fuel cut at deceleration, judge OK if the value is below the threshold value. Judge NG when the malfunction criteria are completed in 2 seconds after the recovery of fuel cut at deceleration which requires 6 seconds or more.

2. Judge NG when the O2 sensor voltage after recovery of fuel cut at deceleration is large. Judge NG when fuel cut at deceleration is also long (6s or more), and although carried out the recovery of fuel cut at deceleration, when O2 sensor voltage is large (more than 0.55 V).




- Normality Judgment
1. Judge Normal When the response time (diagnostic value) is smaller than threshold (judgment value) when oxygen sensor voltage changes from rich to lean, even with or without fuel cut at deceleration.
2. A normal judging is not carried out.
Judge OK when the following standards value are completed.

6. DTC CLEAR CONDITION
- When the OK idling cycle was completed 40 times in a row
- When "Clear Memory" was performed

7. MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle was completed 3 times in a row
- When "Clear Memory" was performed

8. FAIL SAFE
Sub feedback control: Not allowed

9. ECM OPERATION AT DTC SETTING
- Memorize the freeze frame data. (For test mode $02)
- Memorize the diagnostic value and trouble standard value. (For test mode $06)




10. ENABLE CONDITION
- Lean -> Rich response diagnosis

11. GENERAL DRIVING CYCLE
Perform the diagnosis only when fuel cut at deceleration after rapid acceleration. (Pay attention to oxygen sensor voltage for the timing of deceleration.)

12. DIAGNOSTIC METHOD




When the oxygen sensor output voltage changes 0.25 V (lean) to 0.55 V (rich), calculate the Min. value of response time regarded as judgment value while the output varies from 0.3 V to 0.5 V.




- Abnormality Judgment
1. Judge NG when the judgment value is larger than the threshold value after recovery of fuel cut at deceleration.
Response time (Diagnosis time) greater than Threshold value -> Abnormal
2. Judge NG when the O2 sensor voltage after recovery of fuel cut at deceleration is small.




- Normality Judgment
1. Judge Normal When the response time (diagnostic value) is smaller than threshold (judgment value) when oxygen sensor voltage changes from rich to lean, even with or without fuel cut at deceleration.
Response Time (diagnosis value) less than or equal to Threshold value -> Normal
2. A normal judging is not carried out.
Judge OK when the following standards value are completed.

13. DTC CLEAR CONDITION
- When the OK idling cycle was completed 40 times in a row
- When "Clear Memory" was performed

14. MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle was completed 3 times in a row
- When "Clear Memory" was performed

15. FAIL SAFE
Sub feedback control: Not allowed

16. ECM OPERATION AT DTC SETTING
- Memorize the freeze frame data. (For test mode $02)
- Memorize the diagnostic value and trouble standard value. (For test mode $06)