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.

Fig 1: Identifying Oxygen Sensor Output Voltage Graph

Courtesy of SUBARU OF AMERICA, INC.

• 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 
  Fig 2: Threshold Valve Table (1 Of 2)

  Courtesy of SUBARU OF AMERICA, INC.

  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 

  Judge OK when the following standards value are completed.

  Fig 3: Threshold Valve Table (2 Of 2)

  Courtesy of SUBARU OF AMERICA, INC.

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.

Fig 1: Identifying Oxygen Sensor Output Voltage Graph

Courtesy of SUBARU OF AMERICA, INC.

• 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 
  Fig 2: Threshold Valve Table (1 Of 2)

  Courtesy of SUBARU OF AMERICA, INC.

  Time Needed for Diagnosis:  1 time

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

• Normality Judgment 
  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 

  Judge OK when the following standards value are completed.

  Fig 3: Threshold Valve Table (2 Of 2)

  Courtesy of SUBARU OF AMERICA, INC.