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