DTC P0031: Ho2S Heater Control Circuit Low (Bank 1 Sensor 1)

OUTLINE OF DIAGNOSIS
Detect the open or short circuit of front oxygen (A/F) sensor heater.

Diagnosis is performed using A/F microcomputer, and communication is established between A/F microcomputer and main microcomputer. Judge NG when the data of open circuit and shortage NG is transmitted.
COMPONENT DESCRIPTION

Fig 1: Heated Oxygen Sensor Cross Sectional View - Bank 1 Sensor 1
Courtesy of SUBARU OF AMERICA, INC.

ENABLE CONDITION

ENABLE CONDITIONS

Secondary Parameters	Enable Conditions
Battery voltage	10.9 V or more
Heater control	Operation

GENERAL DRIVING CYCLE
Terminate the diagnosis if the open or short circuit becomes NG once by performing diagnosis continuously.

DIAGNOSTIC METHOD

Judge NG when the continuous time of completing all the malfunction criteria below becomes more then 4.5 seconds.

Judgment Value

JUDGMENT VALUE

Time Needed for Diagnosis: 4.5 seconds

Malfunction Indicator Light Illumination: Illuminates as soon as malfunction occurs.

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
None
ECM OPERATION AT DTC SETTING
Memorize the freeze frame data. (For test mode $02)