P0139

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

1. OUTLINE OF DIAGNOSIS
Detect the slow response of the oxygen sensor.
Judge as NG if either the rich to lean response diagnosis or lean to rich response diagnosis is NG, and Judge as OK if both are OK.

[Rich -> Lean diagnosis response]
1. Measure the response time for oxygen sensor output changes when the A/F ratio changes to rich to lean. If the measured response time is larger than the threshold value, it is NG. If it is smaller, it is OK.
2. Judge as NG when the oxygen sensor voltage is large (rich) when recovering from a deceleration fuel cut.

[Lean -> Rich diagnosis response]
1. Measure the response time for oxygen sensor output changes when the A/F ratio changes to lean to rich. If the measured response time is larger than the threshold value, it is NG.
2. Judge as NG when the oxygen sensor voltage remains small when recovering from a deceleration fuel cut.

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




2. COMPONENT DESCRIPTION




3. ENABLE CONDITIONS

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




5. DIAGNOSTIC METHOD
When the rear oxygen sensor output voltage changes from 0.55 V (rich) to 0.25 V (lean), calculate the minimum response time for output change between 0.5 V and 0.3 V for the judgment criteria.

Abnormality Judgment
1. Judge as NG when the judgment value is larger than the threshold value after deceleration fuel cut. Response time (diagnosis value) -> threshold value -> abnormal

NOTE: Variation time of rear oxygen sensor output voltage is short during fuel shut-off in deceleration. NG judgment should be performed with the condition of deceleration fuel cut. Even without deceleration fuel cut, judge as OK if the value is below the threshold.

When the deceleration fuel cut off time is more than 6 seconds, judge as NG if the given criteria are met 2 seconds after recovering from the deceleration fuel cut.




2. Judge as NG when the oxygen sensor voltage at recovery from a deceleration fuel cut, is large. If the fuel cut time in a deceleration fuel cut is long (more than 6 s), and even after recovering from a deceleration fuel cut, the oxygen sensor voltage is high (0.55 V or more), judge as NG.

Normality Judgment
1. Regardless of a deceleration fuel cut, if the response time (diagnosis value) when the oxygen sensor voltage has changed from rich to lean is shorter than the threshold value (judgment value), judge as a normal condition.
Response time (diagnosis value) . threshold value -> normal




2. Do not judge as a normal condition.
Judge as OK when the criteria are met.

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

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

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




12. DIAGNOSTIC METHOD
Calculate the minimum value of 0.3 V to 0.5 V output change response time as judgment value when the rear oxygen sensor output voltage changes from 0.25 V (lean) to 0.55 V (rich).

Abnormality Judgment
1. Judge as NG when the judgment value is larger than the threshold value after deceleration fuel cut.

Response time (diagnosis value) -> threshold value > abnormal




2. If the oxygen sensor voltage is small after recovering from a deceleration fuel cut, and remains small, judge as NG.

Normality Judgment
1. Regardless of a deceleration fuel cut, if the response time (diagnosis value) when the oxygen sensor voltage has changed from rich to lean is shorter than the threshold value (judgment value), judge as a normal condition.
Response time (diagnosis value) . threshold value -> normal




2. Do not judge as a normal condition.
Judge as OK when the criteria below are met.

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

14. MALFUNCTION INDICATOR LIGHT CLEAR CONDITIONS
- When the OK driving cycle is completed 3 times in a row
- When "Clear Memory" is 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)