DTC P0031: A/F / O2 Heater Control Circuit Low Bank 1 Sensor 1 [11/2021 - ]: Procedure

1. Turn the ignition switch to OFF.
2. Disconnect the connector from the air fuel ratio sensor.
3. Turn the ignition switch to ON.
4. Measure the voltage between air fuel ratio sensor connector and engine ground.

   Connector & terminal

   B13-2 - Engine ground

   Is the voltage 10 V or higher?

   Result	Proceed to
   Yes	A
   No (Repair the following item.) Open circuit in harness between No. 1 engine room relay block and No. 1 junction block assembly and air fuel ratio sensor connector Blown out of fuse Poor contact of coupling connector	B

Result: 

B 

REPAIR RELATED PARTS 

Result: 

A 

See step  2

1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Measure the resistance between ECM connector and air fuel ratio sensor connector.

   Connector & terminal

   B1-88 (HTFR1) - B13-1

   Is the resistance less than 1 Ω?

   Result	Proceed to
   Yes	A
   No (Repair the open circuit of harness between ECM connector and air fuel ratio sensor connector.)	B

Result: 

B 

REPAIR HARNESS 

Result: 

A 

See step  3

1. Measure the resistance between air fuel ratio sensor connector and engine ground.

   Connector & terminal

   B13-1 - Engine ground

   Is the resistance 1 MΩ or more?

   Result	Proceed to
   Yes	A
   No (Repair the short circuit to ground in harness between ECM connector and air fuel ratio sensor connector.)	B

Result: 

B 

REPAIR HARNESS 

Result: 

A 

See step  4

1. Measure the resistance of harness between ECM connector and engine ground.

   Connector & terminal

   A5-69 (GNDEG3) - Engine ground

   A5-70 (GNDEG4) - Engine ground

   A5-71 (GNDEG1) - Engine ground

   A5-72 (GNDEG2) - Engine ground

   Is the resistance less than 5 Ω?

   Result	Proceed to
   Yes	A
   No (Repair the following item.) Open circuit of harness between ECM connector and engine ground Poor contact of coupling connector	B

Result: 

B 

REPAIR RELATED PARTS 

Result: 

A 

See step  5

1. Check the air fuel ratio sensor.

   Refer to INSPECTION [11/2021 - ]

   Is the check result OK?

   Result	Proceed to
   Yes (Repair the poor contact of ECM connector.)	A
   No (Replace the air fuel ratio sensor.)	B

Result: 

A 

REPAIR CONNECTOR 

Result: 

B 

REPLACE AIR FUEL RATIO SENSOR. Refer to  REMOVAL [11/2021 - ]