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

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

OUTLINE OF DIAGNOSIS

Detect the slow response of rear oxygen sensor.

Judge NG when the Rich → Lean response diagnosis or Lean → Rich response diagnosis is NG and judge

OK when both response diagnoses are OK.

[Rich → Lean diagnosis response]


1. When the measured response time is larger than a threshold, since the A/F ratio is rich, the response time of the output change of O2 sensor when changing from Rich to Lean is measured, and it judges with NG, and when small, it judges with OK.

2. When O2 sensor voltage at the time of a fuel shut-off in deceleration return is large (rich), it judges with NG.


[Lean → Rich diagnosis response]


1. The response time of output change of O2 sensor when an A/F ratio changes from Lean to Rich is measured, and it is referred to as NG when the measured response time is larger than a threshold.

2. It is referred to as NG when O2 sensor voltage after recovery of fuel shut-off in deceleration is small and still small.


Diagnostic Method

Measure the response time of the output change of the 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


(1)

Atmosphere

(A)

Electromotive force

(D)

Lean

(2)

Exhaust

(B)

Air fuel ratio

(E)

Theoretical air fuel ratio

(3)

Electromotive force

(C)

Rich

(F)

Comparative voltage



ENABLE CONDITION


Rich → Lean response diagnosis

Secondary Parameters Enable Conditions
Battery voltage

> 10.9 V

A/F sub feedback control condition

Completed

6 seconds or more fuel shut-off indecel. time

Experienced

After fuel cut

≥ 2 seconds

Accumulative time of rear oxygen heater current

≥ 60 seconds

Continuous time of rear oxygen heater current

≥ 30 seconds

Catalyst warm-up counter

≥ 8500




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.)

DIAGNOSTIC METHOD

When the oxygen sensor output voltage changes from 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 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 below are completed in 2 seconds after the recovery of fuel shut-off in deceleration which requires 6 seconds or more.

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


Judgment Value

Malfunction Criteria Threshold Value
Shortest time change from rich (500 mV O 2 output) to lean (300 mV) if voltage reduces from 550 mV to 250 mV.

> 0.510 milliseconds

Time when more than 550 mV

> 2 seconds



Time Needed for Diagnosis: 1 time

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

Normality Judgement


1. Judge Normal when the response time (diagnostic value) is smaller than threshold (judgment value) when changing to lean since O2 sensor voltage.

2. A normal judging is not carried out.


Judgment Value

Malfunction Criteria Threshold Value
Change of the shortest time from rich (500 mV02 output), when voltage decreases from 550 mV to 250 mV to lean (300 mV).

≤ 0.510 seconds



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)


ENABLE CONDITION


Lean → Rich response diagnosis

Secondary Parameters Enable Conditions
Battery voltage

> 10.9 V

A/F main feedback control condition

Completed

Fuel cut on deceleration ≥ 6 seconds

Experienced

After fuel cut

≥ 2 seconds




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.)

DIAGNOSTIC METHOD

When the oxygen sensor output voltage changes from 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 shut-off in deceleration.

Response time (Diagnosis value) > Threshold value → Abnormal

2. Judge NG when the O2 sensor voltage after recovery of fuel shut-off in deceleration is small.


Judgment Value

Malfunction Criteria Threshold Value
Shortest time change from lean (300 mV O 2 output) to rich (500 mV) if voltage reduces from 500 mV to 250 mV.

> 2 seconds

Time when less than 250 mV

> 120 seconds



Time Needed for Diagnosis: 1 time

Malfunction Indicator Light Illumination: Illuminates when malfunction occurs in 2 continuous driving cycles.

Normality Judgement


1. Judge Normal when the response time (diagnostic value) is smaller than threshold (judgment value) when changing to lean since O2 sensor voltage.

Response Time (diagnosis value) ≤ Threshold value → Normal

2. A normal judging is not carried out.


Judgment Value

Malfunction Criteria Threshold Value
Change of the shortest time from rich (300 mV02 output), when voltage decreases from 550 mV to 250 mV to lean (500 mV).

≤ 2 seconds



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)