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

/ 9-2X (9346) / 2005 / 2. Engine / ENGINE (DIAGNOSTICS), 2.0T / Diagnostic Procedure with Diagnostic Trouble Code (DTC) / Fault diagnosis, fault codes / DTC P0031 HO2S HEATER CONTROL CIRCUIT LOW (BANK 1 SENSOR 1)

DTC DETECTING CONDITION:

•

Immediately at fault recognition

•

GENERAL DESCRIPTION

Important
After repair or replacement of faulty parts, conduct Clear Memory Mode and Inspection Mode .

WIRING DIAGRAM:

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. 2 (+) — Engine ground (−):

Is the voltage more than 10 V?

Yes

•

Repair the 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

(B84) No. 8 — Chassis ground:

(B84) No. 9 — Chassis ground:

Is the resistance less than 5 Ω?

Yes

•

Repair the harness and connector.

•

Note
In this case, repair the following:
•	Open circuit in harness between ECM and engine ground cable
•	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 the 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

CHECK OUTPUT SIGNAL FROM ECM.

Start and idle the engine.

Measure the voltage between ECM connector and chassis ground.

Connector & terminal

(B84) No. 4 (+) — Chassis ground (−):

(B84) No. 5 (+) — Chassis ground (−):

Is the voltage less than 1 V?

Yes

CHECK OUTPUT SIGNAL FROM ECM.

Measure the voltage between ECM connector and chassis ground.

Connector & terminal

(B84) No. 4 (+) — Chassis ground (−):

(B84) No. 5 (+) — Chassis ground (−):

Shake the ECM harness and connector, while monitoring value of voltage meter. Does the voltage change?

Yes

Repair the poor contact in ECM connector.

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. 2 — No. 1:

Is the resistance less than 10 Ω?

Yes

•

Repair the 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

Replace the front oxygen (A/F) sensor.

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

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

Is the voltage more than 10 V?

CHECK GROUND CIRCUIT OF ECM.

Is the resistance less than 5 Ω?

CHECK CURRENT DATA.

Is the current more than 0.2 A?

CHECK OUTPUT SIGNAL FROM ECM.

Is the voltage less than 1 V?

CHECK OUTPUT SIGNAL FROM ECM.

Shake the ECM harness and connector, while monitoring value of voltage meter. Does the voltage change?

CHECK FRONT OXYGEN (A/F) SENSOR.

Is the resistance less than 10 Ω?

Our Friends