DTC P0037: Ho2S Heater Control Circuit Low (Bank 1 Sensor 2)

Detect open or short circuit of rear oxygen sensor heater.

Rear oxygen sensor heater conducted the duty control, and the output terminal voltage at ON is 0 V and the output terminal voltage at OFF is the battery voltage.

Judge NG when the terminal voltage remains to be Low.

Perform the diagnosis continuously after engine starting.

• Abnormality Judgment 

  Judge NG when the continuous time of completing all the malfunction criteria below becomes more than 2560 millisecond (10 cycles).

  Judgment Value 

  JUDGMENT VALUE CHART
  
  

  Malfunction Criteria	Threshold Value
  Output voltage level	Low
  Rear oxygen sensor heater control duty	< 75%

  Time Needed for Diagnosis:  2.56 seconds

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

• Normality Judgment 

  Judge OK and clear the NG when all the malfunction criteria below are completed.

  Judgment Value 

  JUDGMENT VALUE CHART
  
  

  Malfunction Criteria	Threshold Value
  Output voltage level	High

• When the OK idling cycle was completed 40 times in a row
• When "Clear Memory" was performed

• When the OK driving cycle was completed 3 times in a row
• When "Clear Memory" was performed

Sub feedback control: Not allowed

Memorize the freeze frame data. (For test mode $02)