LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Infiniti >> 2021 >> Q50 Signature Edition, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System (DTCS) (5 Of 6) >> Engine (ECM) >> P2270 O2 Sensor >> DTC Diagnosis Procedure >> VR30DDTT engine
April 5, 2026: LEMON Manuals is launched! Read the announcement.

VR30DDTT engine

  1. INSPECTION START 

    Confirm the detected malfunction (A or B). Refer to DTC Description .

    Which malfunction is detected?

    A

    GO TO 2.

    B

    GO TO 9.

  2. CHECK GROUND CONNECTION 
    1. Turn ignition switch OFF.
    2. Check ground connection E191. Refer to Ground Inspection in Inspection .

    Is the inspection result normal?

    YES

    GO TO 3.

    NO

    Repair or replace ground connection.

  3. CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT 
    1. Disconnect heated oxygen sensor 2 (HO2S2) harness connector.
    2. Disconnect ECM harness connector.
    3. Check the continuity between HO2S2 harness connector and ECM harness connector.

      HO2S2

      ECM

      Continuity

      Bank

      Connector

      Terminal

      Connector

      Terminal

      1

      F125

      4

      F143

      81

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

    Is the inspection result normal?

    YES

    GO TO 4.

    NO

    Repair open circuit, short to ground or short to power in harness or connectors.

  4. CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 
    1. Check the continuity between HO2S2 harness connector and ECM harness connector.

      HO2S2

      ECM

      Continuity

      Bank

      Connector

      Terminal

      Connector

      Terminal

      1

      F125

      3

      F143

      49

      Existed
    2. Check the continuity between HO2S2 harness connector and ground, or ECM harness connector and ground.

      HO2S2

      Ground

      Continuity

      Bank

      Connector

      Terminal

      1

      F125

      3

      Ground

      Not existed

      ECM

      Ground

      Continuity

      Bank

      Connector

      Terminal

      1

      F143

      49

      Ground

      Not existed
    3. Also check harness for short to power.

    Is the inspection result normal?

    YES

    GO TO 5.

    NO

    Repair open circuit, short to ground or short to power in harness or connectors.

  5. CHECK HO2S2 CONNECTOR FOR WATER 

    Check connectors for water.

    Water should not exist.

    Is the inspection result normal?

    YES

    GO TO 6.

    NO

    Repair or replace harness or connectors.

  6. CHECK HEATED OXYGEN SENSOR 2 

    Refer to Component Inspection .

    Is the inspection result normal?

    YES

    GO TO 8.

    NO

    GO TO 7.

  7. REPLACE HEATED OXYGEN SENSOR 2 

    Replace malfunctioning heated oxygen sensor 2.

    CAUTION:
    • Discard any heated oxygen 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 heated oxygen sensor, clean exhaust system threads using Oxygen Sensor Thread Cleaner [commercial service tool (J-43897-18 or J-43897-12)] and approved Anti-seize Lubricant (commercial service tool).

    INSPECTION END

  8. CHECK INTERMITTENT INCIDENT 

    Refer to Inspection .

    INSPECTION END

  9. CHECK GROUND CONNECTION 
    1. Turn ignition switch OFF.
    2. Check ground connection E191. Refer to Ground Inspection in Inspection .

    Is the inspection result normal?

    YES

    GO TO 10.

    NO

    Repair or replace ground connection.

  10. 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 P0172 detected? Is it difficult to start engine?

    YES

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

    NO

    GO TO 11.

  11. CHECK HO2S2 GROUND CIRCUIT FOR OPEN AND SHORT 
    1. Turn ignition switch OFF.
    2. Disconnect heated oxygen sensor 2 harness connector.
    3. Disconnect ECM harness connector.
    4. Check the continuity between HO2S2 harness connector and ECM harness connector.

      HO2S2

      ECM

      Continuity

      Bank

      Connector

      Terminal

      Connector

      Terminal

      1

      F125

      4

      F143

      81

      Existed
    5. Also check harness for short to ground and short to power.

    Is the inspection result normal?

    YES

    GO TO 12.

    NO

    Repair open circuit, short to ground or short to power in harness or connectors.

  12. CHECK HO2S2 INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT 
    1. Check the continuity between HO2S2 harness connector and ECM harness connector.

      HO2S2

      ECM

      Continuity

      Bank

      Connector

      Terminal

      Connector

      Terminal

      1

      F125

      3

      F143

      49

      Existed
    2. Check the continuity between HO2S2 harness connector or ECM harness connector and ground.

      HO2S2

      Ground

      Continuity

      Bank

      Connector

      Terminal

      1

      F125

      3

      Ground

      Not existed

      ECM

      Ground

      Continuity

      Bank

      Connector

      Terminal

      1

      F143

      49

      Ground

      Not existed
    3. Also check harness for short to power.

    Is the inspection result normal?

    YES

    GO TO 13.

    NO

    Repair open circuit, short to ground or short to power in harness or connectors.

  13. CHECK HEATED OXYGEN SENSOR 2 

    Refer to Component Inspection .

    Is the inspection result normal?

    YES

    INSPECTION END

    NO

    Replace malfunctioning heated oxygen sensor 2. Refer to CATALYST : Exploded View .

scientia non olet · About LEMON Manuals