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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.

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


(1)

Atmosphere

(A)

Electromotive force

(2)

Exhaust

(B)

Air fuel ratio

(3)

Electromotive force

(C)

Rich

(D)

Lean

(E)

Theoretical air fuel ratio

(F)

Comparative voltage



ENABLE CONDITION

Secondary Parameters Enable Conditions
Battery voltage

> 10.9 V

A/F sub feedback control condition

Completed

5 seconds or more fuel shut-off in deceleration

Experienced

After fuel cut

≥ 2 seconds

Deterioration diagnosis for rear oxygen sensor response

Not completed

Cumulative time for current conducted in rear oxygen sensor

≥ 60 s

Continuous time for current conducted in rear oxygen sensor

≥ 30 s

Catalyst warm-up counter

≥ 8,000



GENERAL DRIVING CYCLE

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

DIAGNOSTIC METHOD

When the rear 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

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

Judge NG when the malfunction criteria below are completed in 2 seconds after the recovery of fuel shut-off in deceleration which requires 5 seconds or more. Judge OK when the malfunction criteria below are not completed regardless of the fuel shut-off in deceleration.

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.


Judgment Value

Malfunction Criteria Threshold Value
Shortest time change from rich (0.5 V O 2 output) to lean (0.25 V) if voltage reduces from 0.5 V to 0.3 V.

≥ 327 milliseconds



Time Needed for Diagnosis: 10 seconds

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

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)