DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)

DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)

CHECK ANY OTHER DTC ON DISPLAY.

Does the Vehicle Diagnostic Interface or OBD-II general scan tool display DTC P0031 and P0037 at the same time?

Yes

No

CHECK POWER SUPPLY TO FRONT OXYGEN (A/F) SENSOR.

Turn the ignition switch to OFF.

Disconnect the connector from front oxygen (A/F) sensor.

Turn the ignition switch to ON.

Measure the voltage between front oxygen (A/F) sensor connector and engine ground.

Connector & terminal

(B18) No. 6 (+) — Engine ground (−):

Is the voltage more than 10 V?

Yes

No

•	Repair power supply line.

•	Note In this case, repair the following: • Open circuit in harness between main relay and front oxygen (A/F) sensor connector • Poor contact in front oxygen (A/F) sensor connector • Poor contact in main relay connector

CHECK GROUND CIRCUIT OF ECM.

Measure the resistance of harness between ECM connector and chassis ground.

Connector & terminal

(B134) No. 7 — Chassis ground:

(B134) No. 6 — Chassis ground:

Is the resistance less than 5 Ω?

Yes

No

•	Repair harness and connector.

•	Note In this case, repair the following: • Open circuit in harness between ECM and engine ground terminal • Poor contact in ECM connector Poor contact in coupling connector

CHECK CURRENT DATA.

Start the engine.

Read the data of front oxygen (A/F) sensor heater current using Vehicle Diagnostic Interface or OBD-II general scan tool.

Note
•	Vehicle Diagnostic Interface For detailed operation procedure, refer to the “READ CURRENT DATA FOR ENGINE”.
•	OBD-II scan tool For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.

Is the current more than 0.2 A?

Yes

•	Repair poor contact in connector.

•	Note In this case, repair the following: • Poor contact in front oxygen (A/F) sensor connector • Poor contact in ECM connector

No

CHECK INPUT SIGNAL FROM ECM.

Start and idle the engine.

Measure the voltage between ECM connector and chassis ground.

Connector & terminal

(B134) No. 3 (+) — Chassis ground (−):

(B134) No. 2 (+) — Chassis ground (−):

Is the voltage less than 1 V?

Yes

No

CHECK OUTPUT SIGNAL FROM ECM.

Measure the voltage between ECM connector and chassis ground.

Connector & terminal

(B134) No. 3 (+) — Chassis ground (−):

(B134) No. 2 (+) — Chassis ground (−):

Does the voltage change by shaking the ECM harness and connector?

Yes

Repair poor contact in ECM connector.

No

CHECK FRONT OXYGEN (A/F) SENSOR.

Turn the ignition switch to OFF.

Measure the resistance between front oxygen (A/F) sensor connector terminals.

Terminals

No. 4 — No. 6:

Is the resistance less than 10 Ω?

Yes

•	Repair harness and connector.

•	Note In this case, repair the following: • Open or ground short circuit in harness between front oxygen (A/F) sensor and ECM connector • Poor contact in front oxygen (A/F) sensor connector • Poor contact in ECM connector

No

Replace the front oxygen (A/F) sensor.