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Nissan Sentra B18 (2020-2025) Service Manual: P0031 A/f Sensor 1 Heater

Dtc Description

DTC Description

DTC DETECTION LOGIC

DTC

CONSULT screen terms

(Trouble diagnosis content)

DTC detection condition

P0031

A/F SEN1 HTR (B1)

(HO2S heater control circuit low bank 1 sensor 1)

Diagnosis condition

Engine running at idle

Signal (terminal)

A/F sensor 1 heater signal

Threshold

An excessively low voltage signal is sent to ECM through the A/F sensor 1 heater

Diagnosis delay time

—

POSSIBLE CAUSE

  • Harness or connectors (The A/F sensor 1 heater circuit is open or shorted.)

  • The A/F sensor 1 heater

FAIL-SAFE

Not applicable

Confirmation Procedure

Confirmation Procedure

  1. PRECONDITIONING

    If DTC Confirmation Procedure has been previously conducted, always turn ignition switch OFF and wait at least 10 seconds before conducting the next test.

    TESTING CONDITION:

    Before performing the following procedure, confirm that battery voltage is 11 V or more at idle.

    >>

    GO TO 2.

  2. PERFORM DTC CONFIRMATION PROCEDURE

    1. Start the engine and let it idle for at least 10 seconds.

    2. Check 1st trip DTC.

    Is 1st trip DTC detected?

    YES >>

    Proceed to DTC Diagnosis Procedure.

    NO-1 >>

    To check malfunction symptom before repair: Refer to Intermittent Incident.

    NO-2 >>

    Confirmation after repair: INSPECTION END

Dtc Diagnosis Procedure

DTC Diagnosis Procedure

  1. CHECK AIR FUEL RATIO (A/F) SENSOR 1 POWER SUPPLY

    1. Turn ignition switch OFF.

    2. Disconnect air fuel ratio (A/F) sensor 1 harness connector.

    3. Turn ignition switch ON.

    4. Check the voltage between A/F sensor 1 harness connector and ground.

      +

      −

      Voltage

      A/F sensor 1

      Connector

      Terminal

      F12

      4

      Ground

      Battery voltage

    Is the inspection result normal?

    YES >>

    GO TO 3.

    NO >>

    GO TO 2.

  2. CHECK A/F SENSOR 1 POWER SUPPLY CIRCUIT

    1. Turn ignition switch OFF.

    2. Disconnect IPDM E/R harness connector.

    3. Check the continuity between A/F sensor 1 harness connector and IPDM E/R harness connector.

      A/F sensor 1

      IPDM E/R

      Continuity

      Connector

      Terminal

      Connector

      Terminal

      F12

      4

      F96

      75

      Existed

    Is the inspection result normal?

    YES >>

    Perform the trouble diagnosis for power supply circuit.

    NO >>

    Repair or replace malfunctioning part.

  3. CHECK A/F SENSOR 1 HEATER OUTPUT SIGNAL CIRCUIT

    1. Turn ignition switch OFF.

    2. Disconnect ECM harness connector.

    3. Check the continuity between A/F sensor 1 harness connector and ECM harness connector.

      A/F sensor 1

      ECM

      Continuity

      Connector

      Terminal

      Connector

      Terminal

      F12

      3

      F25

      126

      Existed

    4. Also check harness for short to ground and short to power.

    Is the inspection result normal?

    YES >>

    GO TO 4.

    NO >>

    Repair or replace malfunctioning part.

  4. CHECK A/F SENSOR 1 HEATER

    Refer to Component Inspection.

    Is the inspection result normal?

    YES >>

    INSPECTION END

    NO >>

    GO TO 5.

  5. REPLACE A/F SENSOR 1

    Replace A/F sensor 1. Refer to Exploded View.

    CAUTION:

    • Discard any A/F sensor which has been dropped from a height of more than 0.5 m (19.7 in) onto a hard surface such as a concrete floor; use a new one.

    • Before installing new A/F sensor, clean exhaust system threads.

    >>

    INSPECTION END

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