P0139
DTC P0139 - O2 SENSOR CIRCUIT SLOW RESPONSE (BANK 1 SENSOR 2)OUTLINE OF DIAGNOSIS
Detect the slow response of rear oxygen sensor.
Calculate the response time of the output change of the rear oxygen sensor when the A/F ratio changes from rich to lean. And carry out the diagnosis comparing the calculated response time with the threshold value.
COMPONENT DESCRIPTION
ENABLE CONDITION
GENERAL DRIVING CYCLE
Perform the diagnosis only once during fuel cut at deceleration from the rapid acceleration. (Pay attention to oxygen sensor voltage when deciding the deceleration timing to calculate the diagnostic value.)
DIAGNOSTIC METHOD
When the rear oxygen sensor output voltage changes from 0.5 V (rich) to 0.15V (lean), carry out calculation regarding the response time of the output change from 0.45 V to 0.2 V as diagnostic value. When the rear oxygen sensor output voltage does not change from 0.5 V to 0.15 V, do not carry out calculation even if the output changes from 0.45 V to 0.2 V.
- Abnormality Judgment
Judge NG when the rear oxygen sensor output change response time (diagnostic value) exceeds the threshold value.
Response time > 2 seconds (threshold value) -> Abnormal
Judge NG when all of the malfunction criteria is completed.
- Normality Judgment
Judge OK when the rear oxygen sensor output change response time (diagnostic value) is below the threshold value.
Response time <= 2 seconds (threshold value) -> Normal
Judge NG when the malfunction criteria is completed.
NOTE: Response time is calculated during the deceleration fuel cut in case of abnormal judgment. However, in order to make a normal judgment quickly, diagnosis is performed without deceleration fuel cut.
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
None
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)