Diagnostic Method

When the oxygen sensor output voltage changes 0.5 V (rich) to 0.15 V (lean), calculate the Min. value of response time regarded as

Fig 1: Oxygen Sensor Voltage Output Graph

Courtesy of SUBARU OF AMERICA, INC.

• Abnormality Judgment 
  1. Judge NG when the judgment value is larger than the threshold value after fuel cut at deceleration. Response time (Diagnosi value) > Threshold value → Abnormal
     NOTE: Variation time of rear oxygen sensor output voltages is short during fuel cut at deceleration. Carry out the NG judgment only after the fuel cut at deceleration. As for OK judgment, without the condition of fuel cut at 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 cut at deceleration which requires 2 seconds or more.

  2. Judge NG when the O₂ sensor voltage after recovery of fuel cut at deceleration is large. Judge NG when fuel cut at deceleration is also long (2s or more), and although carried out the recovery of fuel cut at deceleration, when O₂ sensor voltage is large (more than 0.5V).
• Judgment Value 
  JUDGMENT VALUE (ABNORMALITY JUDGMENT)
  
  

  Malfunction Criteria	Threshold Value
  Shortest time change from rich (450 mV O2 output) to lean (200 mV) if voltage reduces from 500 mV to 150 mV.	> 0.53 seconds
  Or, longest time when more than 500 mV	> 2 seconds

Time Needed for Diagnosis  : 4 seconds

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 oxygen sensor voltage changes from rich to lean, even with or without fuel cut at deceleration.
  2. A normal judging is not carried out.
• Judgment Value 

  Judge OK when the following standards value are completed.

  JUDGMENT VALUE (NORMALITY JUDGMENT)
  
  

  Malfunction Criteria	Threshold Value
  Shortest time change from rich (450 mV O2 output) to lean (200 mV) if voltage reduces from 500 mV to 150 mV.	≤ 0.53 seconds

When the oxygen sensor output voltage changes 0.15 V (lean) to 0.5 V (rich), calculate the Min. value of response time regarded as

Fig 1: Oxygen Sensor Voltage Output 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 cut at deceleration.

     Response time (Diagnosis time) > Threshold value → Abnormal

  2. Judge NG when the O₂ sensor voltage after recovery of fuel cut at deceleration is small.
• Judgment Value 
  JUDGMENT VALUE (ABNORMALITY JUDGMENT)
  
  

  Malfunction Criteria	Threshold Value
  Shortest time change from lean (200 mV O2 output) to rich (450 mV) if voltage increases from 150 mV to 500 mV.	≥ 2 seconds
  Or, longest time of 150 mV or less	≥ 120 seconds

Time Needed for Diagnosis  : 124 seconds

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 oxygen sensor voltage changes from rich to lean, even with or without fuel cut at deceleration.

     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.

  JUDGMENT VALUE (NORMALITY JUDGMENT)
  
  

  Malfunction Criteria	Threshold Value
  Shortest time change from lean (200 mV O2 output) to rich (450 mV) if voltage increases from 150 mV to 500 mV.	< 2 seconds