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Nissan Versa
 Sedan Service Manual
Engine » Engine control system (EC) » P0138 HO2s2
DTC Logic

DTC DETECTION LOGIC

The heated oxygen sensor 2 has a much longer switching time between rich and lean than the air fuel ratio (A/ F) sensor 1. The oxygen storage capacity of the three way catalyst 1 causes the longer switching time.

MALFUNCTION A

To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the voltage is unusually high during various driving conditions such as fuel cut.

MALFUNCTION A

MALFUNCTION B

To judge the malfunctions of heated oxygen sensor 2, ECM monitors whether the minimum voltage of sensor is sufficiently low during various driving conditions such as fuel cut.

MALFUNCTION B

DTC No. Trouble diagnosis name DTC detecting condition Possible cause
P0138 Heated oxygen sensor 2 circuit high voltage A An excessively high voltage from the sensor is sent to ECM.
  • Harness or connectors (The sensor circuit is open or shorted)
  • Heated oxygen sensor 2
B The minimum voltage from the sensor is not reached to the specified voltage.
  • Harness or connectors (The sensor circuit is open or shorted)
  • Heated oxygen sensor 2
  • Fuel pressure
  • Fuel injector

DTC CONFIRMATION PROCEDURE

1.PRECONDITIONING OF DTC CONFIRMATION PROCEDURE FOR MALFUNCTION A

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.

>> GO TO 2.

2.PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION A

  1. Start engine and warm it up to normal operating temperature.
  2. Turn ignition switch OFF and wait at least 10 seconds.
  3. Start engine and keep the engine speed between 3,500 and 4,000 rpm for at least 1 minute under no load.
  4. Let engine idle for 2 minutes.
  5. Check 1st trip DTC.

Is 1st trip DTC detected?

YES >> Proceed to EC, "Diagnosis Procedure".

NO1 >> With CONSULT: GO TO 3.

NO2 >> Without CONSULT: GO TO 5.

3.PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION B

NOTE: For better results, perform "DTC WORK SUPPORT" at a temperature of 0 to 30C (32 to 86F).

  1. Turn ignition switch ON and select "DATA MONITOR" mode of "ENGINE" using CONSULT.
  2. Start engine and warm it up to normal operating temperature.
  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. Make sure that "COOLAN TEMP/S" indication is more than 70C (158F).

    If not, warm up engine and go to next step when "COOLAN TEMP/S" indication reaches 70C (158F).

  7. Open engine hood.
  8. Select "HO2S2 (B1) P1146" of "HO2S2" in "DTC WORK SUPPORT" mode of "ENGINE" using CONSULT.
  9. Follow the instruction of CONSULT.

    NOTE: It will take at most 10 minutes until "COMPLETED" is displayed.

  10. Touch "SELFDIAG RESULT".

Which is displayed on CONSULT

OK >> INSPECTION END

NG >> Proceed to EC, "Diagnosis Procedure".

CAN NOT BE DIAGNOSED>>GO TO 4.

4.PERFORM DTC CONFIRMATION PROCEDURE FOR MALFUNCTION B AGAIN

  1. Turn ignition switch OFF and leave the vehicle in a cool place (soak the vehicle).
  2. Perform DTC confirmation procedure again.

>> GO TO 3.

5.PERFORM COMPONENT FUNCTION CHECK FOR MALFUNCTION B

Perform component function check. Refer to EC, "Component Function Check".

NOTE: Use component function check to check the overall function of the heated oxygen sensor 2 circuit. During this check, a 1st trip DTC might not be confirmed.

Is the inspection result normal?

YES >> INSPECTION END

NO >> Proceed to EC, "Diagnosis Procedure".

    More about «P0138 HO2s2»:

    DTC Logic

    Component Function Check

    Diagnosis Procedure

    Component Inspection

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