Nissan Sentra B18 (2020-2025) Service Manual: P014c A/f Sensor 1

Dtc Description

To judge malfunctions, this diagnosis measures response time of the A/F signal computed by ECM from the A/F sensor 1 signal. The time is compensated by engine operating (speed and load), fuel feedback control constant, and the A/F sensor 1 temperature index. Judgment is based on whether the compensated time (the A/F signal cycling time index) is inordinately long or not.

DTC DETECTION LOGIC

POSSIBLE CAUSE

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

• A/F sensor 1

FAIL-SAFE

Not applicable

Confirmation Procedure

1. PRECONDITIONING

   If DTC Confirmation Procedure has been previously conducted, always perform the following procedure before conducting the next test.

   1. Turn ignition switch OFF and wait at least 10 seconds.

   2. Turn ignition switch ON.

   3. Turn ignition switch OFF and wait at least 10 seconds.

   TESTING CONDITION:

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

   Do you have CONSULT?

   YES >>

   GO TO 2.

   NO >>

   GO TO 6.

2. PERFORM DTC CONFIRMATION PROCEDURE-1

   With CONSULT

   1. Start engine and warm it up to normal operating temperature.

   2. Turn ignition switch OFF and wait at least 10 seconds.

   3. Turn ignition switch ON.

   4. Turn ignition switch OFF and wait at least 10 seconds.

   5. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1minute under no load.

   6. Let engine idle for 1 minute.

   7. Increase the engine speed up to about 3,600 rpm and keep it for 10 seconds.

   8. Fully release accelerator pedal and then let engine idle for about 1 minute.

   9. Check the items status of “DATA MONITOR” as follows.

      Note:

      If “PRSNT” changed to “ABSNT”, refer to Component Function Check.

      Data monitor item	Status
      A/F SEN1 DIAG3 (B1)	PRSNT

   Is “PRSNT” displayed on CONSULT screen?

   YES >>

   GO TO 4.

   NO >>

   GO TO 3.

3. PERFORM DTC CONFIRMATION PROCEDURE-2

   With CONSULT

   Perform DTC confirmation procedure-1 again.

   Is “PRSNT” displayed on CONSULT screen?

   YES >>

   GO TO 4.

   NO >>

   Refer to Component Function Check.

4. PERFORM DTC CONFIRMATION PROCEDURE-2

   With CONSULT

   1. Wait for about 20 seconds at idle.

   2. Check the items status of “DATA MONITOR” as follows.

      Note:

      If “CMPLT” changed to “INCMP”, refer to Component Function Check.

      Data monitor item	Status
      A/F SEN1 DIAG1 (B1)	CMPLT
      A/F SEN1 DIAG2 (B1)

   Is “CMPLT” displayed on CONSULT screen?

   YES >>

   GO TO 5.

   NO >>

   Refer to DTC Diagnosis Procedure.

5. PERFORM SELF-DIAGNOSIS

   With CONSULT

   Check the “SELF-DIAG RESULT”.

   Is any DTC detected?

   YES >>

   Proceed to DTC Diagnosis Procedure.

   NO >>

   INSPECTION END

6. CHECK AIR-FUEL RATIO SELF-LEARNING VALUE

   With GST

   1. Start engine and warm it up to normal operating temperature.

   2. Select Service $01 with GST.

   3. Calculate the total value of “Short term fuel trim” and “Long term fuel trim” indications.

   Is the total percentage within ±15%?

   YES >>

   GO TO 8.

   NO >>

   GO TO 7.

7. DETECT MALFUNCTIONING PART

   Check the following.

   • Intake air leaks

   • Exhaust gas leaks

   • Incorrect fuel pressure

   • Lack of fuel

   • Fuel injector

   • Incorrect PCV hose connection

   • PCV valve

   • Mass air flow sensor

   >>

   Repair or replace malfunctioning part.

8. PERFORM DTC CONFIRMATION PROCEDURE

   1. Turn ignition switch OFF and wait at least 10 seconds.

   2. Turn ignition switch ON.

   3. Turn ignition switch OFF and wait at least 10 seconds.

   4. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.

   5. Let engine idle for 1 minute.

   6. Increase the engine speed up to about 3,600 rpm and keep it for 10 seconds.

   7. Fully release accelerator pedal and then let engine idle for about 1 minute.

   8. 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

1. RETIGHTEN A/F SENSOR 1

   Loosen and retighten the A/F sensor 1. Refer to Exploded View.

   >>

   GO TO 2.

2. CHECK EXHAUST GAS LEAK

   1. Start engine and run it at idle.

   2. Listen for an exhaust gas leak before three way catalyst (manifold).

      

   Is exhaust gas leak detected?

   YES >>

   Repair or replace.

   NO >>

   GO TO 3.

3. CHECK FOR INTAKE AIR LEAK

   Listen for an intake air leak after the mass air flow sensor.

   Is intake air leak detected?

   YES >>

   Repair or replace.

   NO >>

   GO TO 4.

4. CLEAR THE MIXTURE RATIO SELF-LEARNING VALUE

   1. Clear the mixture ratio self-learning value. Refer to Work Procedure.

   2. Run engine for at least 10 minutes at idle speed.

   Is the 1st trip DTC P0171 or P172 detected? Is it difficult to start engine?

   YES >>

   Perform trouble diagnosis for DTC P0171 or P0172. Refer to DTC Description. or Refer to DTC Description.

   NO >>

   GO TO 5.

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

   1. Disconnect A/F sensor 1 harness connector.

   2. Turn ignition switch ON.

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

      A/F sensor 1		Ground	Voltage
      Connector	Terminal
      F12	4	Ground	Battery voltage

   Is the inspection result normal?

   YES >>

   GO TO 6.

   NO >>

   Repair or replace error-detected parts.

6. CHECK A/F SENSOR 1 INPUT 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	1	F25	86	Existed
      	2		88

   4. Check the continuity between A/F sensor 1 harness connector and ground, or ECM harness connector and ground.

      A/F sensor 1		Ground	Continuity
      Connector	Terminal
      F12	1	Ground	Not existed
      	2

      ECM		Ground	Continuity
      Connector	Terminal
      F25	86	Ground	Not existed
      	88

   5. Also check harness for short to power.

   Is the inspection result normal?

   YES >>

   GO TO 7.

   NO >>

   Repair or replace error-detected parts.

7. CHECK AIR FUEL RATIO (A/F) SENSOR 1 HEATER

   Refer to Component Inspection.

   Is the inspection result normal?

   YES >>

   GO TO 8.

   NO >>

   GO TO 10.

8. CHECK MASS AIR FLOW SENSOR

   Refer to Component Inspection.

   Is the inspection result normal?

   YES >>

   GO TO 9.

   NO >>

   Replace mass air flow sensor. Refer to Exploded View.

9. CHECK PCV VALVE

   Refer to POSITIVE CRANKCASE VENTILATION : Periodic Maintenance.

   Is the inspection result normal?

   YES >>

   GO TO 10.

   NO >>

   Repair or replace PCV valve. Refer to Component Parts Location.

10. REPLACE AIR FUEL RATIO (A/F) SENSOR 1

    Replace air fuel ratio (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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