P0139
DTC P0139 - O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2)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.
COMPONENT DESCRIPTION
ENABLE CONDITION
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 calculate the diagnostic value.)
DIAGNOSTIC METHOD
When the rear oxygen sensor output voltage changes from 0.5 V (rich) to 0.2 V (lean), calculate the Min. value of response time regarded as judgment value while the output varies from 0.45 V to 0.25 V.
- Abnormality Judgment
Judge NG when the judgment value is larger than the threshold value after fuel shut-off in deceleration. Response time (Diagnosis value) -> Threshold value -> Abnormal
NOTE: Variation time of rear oxygen sensor output voltage is short during fuel shut-off in deceleration. Carry out the NG judgment only after the fuel shut-off in deceleration. As for OK judgment, without the condition of fuel shut-off in deceleration, judge OK if the value is below the threshold value. Judge NG when the malfunction criteria are completed in 5 seconds after the recovery of fuel shut-off in deceleration which requires 5 seconds or more. Judge OK when the malfunction criteria are not completed regardless of the fuel shut-off in deceleration.
- Judgment Value
Judge NG when the malfunction criteria are completed.
DTC CLEAR CONDITION
- When the OK idling cycle was completed 40 times in a row
- When "Clear Memory" was performed
MALFUNCTION INDICATOR LIGHT CLEAR CONDITION
- When the OK driving cycle was completed 3 times in a row
- When "Clear Memory" was performed
FAIL SAFE
Sub feedback control: Not allowed
ECM OPERATING AT DTC SETTING
- Memorize the freeze frame data. (For test mode $02)
- Memorize the diagnostic value and trouble standard value. (For test mode $06)