SFI SYSTEM, Diagnostic DTC:P0136, P0137, P0138

DTC Code DTC Name
P0136 Oxygen Sensor Circuit Malfunction (Bank 1 Sensor 2)
P0137 Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0138 Oxygen Sensor Circuit High Voltage (Bank 1 Sensor 2)

DESCRIPTION

Tech Tips

Sensor 2 refers to the sensor mounted behind the three way catalytic converter and located far from the engine assembly.

A three way catalyst converter is used in order to convert the carbon monoxide, hydrocarbons, and nitrogen oxide, into less harmful substances. To allow the three way catalytic converter to function effectively, it is necessary to keep the air fuel ratio of the engine near the stoichiometric air fuel ratio. For the purpose of helping the ECM to deliver accurate air fuel ratio control, a heated oxygen sensor is used.

The heated oxygen sensor is located behind the three way catalytic converter, and detects the oxygen concentration in the exhaust gas. Since the sensor is integrated with the heater that heats the sensing portion, it is possible to detect the oxygen concentration even when the intake air volume is low (the exhaust gas temperature is low).

When the air fuel ratio becomes lean, the oxygen concentration in the exhaust gas is rich. The heated oxygen sensor informs the ECM that the post-three way catalytic converter air fuel ratio is lean (low voltage, i.e. less than 0.45 V).

Conversely, when the air fuel ratio is richer than the stoichiometric air fuel level, the oxygen concentration in the exhaust gas becomes lean. The heated oxygen sensor informs the ECM that the post-three way catalytic converter air fuel ratio is rich (high voltage, i.e. more than 0.45 V). The heated oxygen sensor has the property of changing its output voltage drastically when the air fuel ratio is close to the stoichiometric level.

The ECM uses the supplementary information from the heated oxygen sensor to determine whether the air fuel ratio after the three way catalytic converter is rich or lean, and adjusts the fuel injection time accordingly. Thus, if the heated oxygen sensor is working improperly due to internal malfunctions, the ECM is unable to compensate for deviations in the primary air fuel ratio control.

A005U5CE01
DTC No. DTC Detection Condition Trouble Area
P0136

  • Abnormal voltage output:

    During active air fuel ratio control, following conditions (a) and (b) are met for certain period of time (2 trip detection logic):


    • (a) Heated oxygen sensor voltage not decrease to less than 0.21 V


    • (b) Heated oxygen sensor voltage not increase to more than 0.59 V

  • Open or short in heated oxygen sensor (sensor 2) circuit

  • Heated oxygen sensor (sensor 2)

  • Air fuel ratio sensor (sensor 1)

  • Gas leak from exhaust system
P0137

  • Low voltage (open):

    During active air fuel ratio control, following conditions (a) and (b) are met for certain period of time (2 trip detection logic):


    • (a) Heated oxygen sensor voltage output less than 0.21 V


    • (b) Target air fuel ratio rich

  • Open in heated oxygen sensor (sensor 2) circuit

  • Heated oxygen sensor (sensor 2)

  • Gas leak from exhaust system
P0138

  • High voltage (short):

    During active air fuel ratio control, following conditions (a) and (b) are met for certain period of time (2 trip detection logic):


    • (a) Heated oxygen sensor voltage output 0.59 V or more


    • (b) Target air fuel ratio lean

  • Short in heated oxygen sensor (sensor 2) circuit

  • Heated oxygen sensor (sensor 2)

  • Air fuel ratio sensor (sensor 1)

  • ECM

WIRING DIAGRAM

Refer to DTC P2195 Click here.

CONFIRMATION DRIVING PATTERN

Tech Tips


  • This confirmation driving pattern is used in the "Perform Confirmation Driving Pattern" procedure of the following diagnostic troubleshooting procedure.

  • Performing this confirmation pattern will activate the heated oxygen sensor monitor. (The catalyst monitor is performed simultaneously.) This is very useful for verifying the completion of the repair.

A005RQWE31

  1. Connect the intelligent tester to the DLC3.

  2. Turn the ignition switch to ON.

  3. Turn the tester on.

  4. Enter the following menus: Powertrain / Engine and ECT / DTC / Clear.

  5. Clear DTCs.

  6. Start the engine and warm it up (Procedure "A").

  7. Drive the vehicle at between 90 km/h and 110 km/h (56 mph and 68 mph) for at least 10 minutes (Procedure "B").

  8. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

  9. Input DTCs: P0136, P0137 and P0138.

  10. Check that DTC MONITOR is NORMAL. If DTC MONITOR is INCOMPLETE, perform the drive pattern adding the vehicle speed.

INSPECTION PROCEDURE

Tech Tips

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F sensor function provided in the Active Test. The Control the Injection Volume for A/F sensor function can help to determine whether the Air-Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for A/F sensor operation using the intelligent tester.


  1. Connect the intelligent tester to the DLC3.

  2. Start the engine and turn the tester on.

  3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

  4. On the tester, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.

  5. Perform the Active Test operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

  6. Monitor the output voltages of the A/F and HO2 sensors (AFS Voltage B1 S1 and O2S B1 S2) displayed on the tester.

Tech Tips


  • The Control the Injection Volume for A/F sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.

  • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

Tester Display (Sensor) Injection Volume Status Voltage

AFS Voltage B1 S1

(A/F)

 +25% Rich Below 3.1 V

AFS Voltage B1 S1

(A/F)

 -12.5% Lean Higher than 3.4 V

O2S B1 S2

(HO2)

 +25% Rich Higher than 0.55 V

O2S B1 S2

(HO2)

 -12.5% Lean Below 0.4 V

Note

The air fuel ratio sensor has an output delay of a few seconds and the heated oxygen sensor has a maximum output delay of approximately 20 seconds.

Case A/F Sensor (Sensor 1) Output Voltage HO2 Sensor (Sensor 2) Output Voltage Main Suspected Trouble Area
1 A005SFCE01 A005W6XE08 A005SFCE01 A005R6EE06 -
2 A005SFCE01 A005S6BE01 A005SFCE01 A005R6EE06

  • A/F sensor

  • A/F sensor heater

  • A/F sensor circuit
3 A005SFCE01 A005W6XE08 A005SFCE01 A005S6BE01

  • HO2 sensor

  • HO2 sensor heater

  • HO2 sensor circuit
4 A005SFCE01 A005S6BE01 A005SFCE01 A005S6BE01

  • Injector

  • Fuel pressure

  • Gas leak from exhaust system (Air-fuel ratio extremely rich or lean)

Note

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

Tech Tips

Read freeze frame data using an intelligent tester. Freeze frame data records the engine condition when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.

PROCEDURE


  1. READ OUTPUT DTC (DTC P0136, P0137 OR P0138)


    1. Connect an intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Enter the following menus: Powertrain / Engine and ECT / DTC.

    5. Read DTCs.

      Result
      Display (DTC Output) Proceed to
      P0138 A
      P0137 B
      P0136 C

    B

    CHECK EXHAUST GAS LEAK Click here

    C

    READ VALUE USING INTELLIGENT TESTER (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR) Click here

    A

  2. READ VALUE USING INTELLIGENT TESTER (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)


    1. Connect an intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Enter the following menus: Powertrain / Engine and ECT / Data List / O2S B1 S2.

    5. Allow the engine to idle.

    6. Read the heated oxygen sensor output voltage while idling.

      Result
      Heated oxygen sensor output voltage Proceed to
      1.0 V or higher A
      Below 1.0 V B

    B

    PERFORM ACTIVE TEST USING INTELLIGENT TESTER (INJECTOR VOLUME) Click here

    A

  3. INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)


    1. A005T1XE03
      Text in Illustration
      *1

      Component without harness connected

      (Heated Oxygen Sensor)

      Disconnect the heated oxygen sensor connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      2 (+B) - 3 (OX1B) Always 10 kΩ or higher
      2 (+B) - 4 (E2) Always 10 kΩ or higher

    3. Reconnect the heated oxygen sensor connector.


    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)


    1. A005T37E55
      Text in Illustration
      *1

      Front view of wire harness connector

      (to ECM)

      Turn the ignition switch off and wait for 5 minutes.

    2. Disconnect the ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      B39-63 (HT1B) - B39-80 (OX1B) Always 10 kΩ or higher

    4. Reconnect the ECM connector.


    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - HEATED OXYGEN SENSOR)

    OK

    REPLACE ECM Click here

  5. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (INJECTOR VOLUME)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine.

    3. Turn the tester on.

    4. Warm up the engine.

    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.

    6. Change the fuel injection volume using the tester, and monitor the voltage output of the air fuel ratio sensor and heated oxygen sensor displayed on the tester.

      Tech Tips


      • Change the fuel injection volume within the range of -12% and +12%. The injection volume can be changed in 0.2% graduations within this range.

      • The air fuel ratio sensor is displayed as AFS Voltage B1 S1, and the heated oxygen sensor is displayed as O2S B1 S2 on the intelligent tester.

      Result
      Tester Display (Sensor) Voltage Variation Proceed to
      AFS Voltage B1 S1 (A/F) Alternates between more and less than 3.25 V OK
      AFS Voltage B1 S1 (A/F) Remains at more than 3.25 V NG
      AFS Voltage B1 S1 (A/F) Remains at less than 3.25 V NG

      Tech Tips

      A normal heated oxygen sensor voltage (O2S B1 S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor voltage remains at either less or more than 3.25 V despite the heated oxygen sensor indicating a normal reaction, the air fuel ratio sensor is malfunctioning.

      A005RV4E21

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

    OK

  6. INSPECT AIR FUEL RATIO SENSOR

    Tech Tips

    This air fuel ratio sensor test is to check the air fuel ratio sensor current during the fuel-cut operation. When the sensor is normal, the sensor current will indicate below 3.0 mA in this test.


    1. Connect an intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Drive the vehicle by the drive pattern as listed below:


      1. Warm up the engine until the engine coolant temperature reaches 75°C (167°F) or more.

      2. Drive the vehicle at 60 km/h (40 mph) or more and decelerate the vehicle for 5 seconds or more.

      3. Repeat the deceleration above at least 3 times.

        A005SUJE27

    5. Enter the following menus: Powertrain / Engine and ECT / Data List / AFS Current B1 S1.

    6. Read the value of the air fuel ratio sensor current while the fuel-cut operation is performing.

      Standard Current
      Less than 3.0 mA

      Tech Tips


      • To measure the air fuel ratio sensor current precisely, perform the fuel-cut operation as long as possible.

      • If it is difficult to measure the air fuel ratio sensor current, use the snapshot function of the intelligent tester.


    OK

    REPLACE HEATED OXYGEN SENSOR Click here

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

  7. READ VALUE USING INTELLIGENT TESTER (OUTPUT VOLTAGE OF HEATED OXYGEN SENSOR)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Start the engine.

    5. Enter the following menus: Powertrain / Engine and ECT / Data List / O2S B1 S2.

    6. After warming up the engine, run the engine at an engine speed of 2500 rpm for 3 minutes.

    7. Read the output voltage of the heated oxygen sensor when the engine speed is suddenly increased.

      Tech Tips

      Quickly accelerate the engine to 4000 rpm 3 times using the accelerator pedal.

      Standard Voltage
      Fluctuates between 0.4 V or less and 0.5 V or more.

    NG

    CHECK EXHAUST GAS LEAK Click here

    OK

  8. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (INJECTION VOLUME)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine.

    3. Turn the tester on.

    4. Warm up the engine.

    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.

    6. Change the fuel injection volume using the tester, and monitor the voltage output of the air fuel ratio sensor and heated oxygen sensor displayed on the tester.

      Tech Tips


      • Change the fuel injection volume within the range of -12% and +12%. The injection volume can be changed in 0.2% graduations within this range.

      • The air fuel ratio sensor is displayed as AFS Voltage B1 S1, and the heated oxygen sensor is displayed as O2S B1 S2 on the intelligent tester.

      Result
      Tester Display (Sensor) Voltage Variation Proceed to
      AFS Voltage B1 S1 (A/F) Alternates between more and less than 3.25 V OK
      AFS Voltage B1 S1 (A/F) Remains at more than 3.25 V NG
      AFS Voltage B1 S1 (A/F) Remains at less than 3.25 V NG

      Tech Tips

      A normal heated oxygen sensor voltage (O2S B1 S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor voltage remains at either less or more than 3.25 V despite the heated oxygen sensor indicating a normal reaction, the air fuel ratio sensor is malfunctioning.

      A005RV4E21

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

    OK

    CHECK EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO AND REPAIR CAUSE (FUEL INJECTOR, FUEL PRESSURE, GAS LEAK FROM SYSTEM, ETC.) Click here

  9. CHECK EXHAUST GAS LEAK


    1. Check for exhaust gas leakage.

      OK
      No gas leakage.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

    OK

  10. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)


    1. A005T1XE03
      Text in Illustration
      *1

      Component without harness connected

      (Heated Oxygen Sensor)

      Disconnect the heated oxygen sensor connector.

    2. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      1 (HT1B) - 2 (+B) 20°C (68°F) 11 to 16 Ω
      1 (HT1B) - 4 (E2) Always 10 kΩ or higher

    3. Reconnect the heated oxygen sensor connector.


    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

  11. CHECK HARNESS AND CONNECTOR (HEATED OXYGEN SENSOR - ECM)


    1. A005UKLE04
      Text in Illustration
      *1

      Front view of wire harness connector

      (to Heated Oxygen Sensor)
      *2

      Front view of wire harness connector

      (to ECM)

      Disconnect the heated oxygen sensor connector.

    2. Disconnect the ECM connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance (Check for open)
      Tester Connection Condition Specified Condition
      B25-1 (HT1B) - B39-63 (HT1B) Always Below 1 Ω
      B25-3 (OX1B) - B39-80 (OX1B) Always Below 1 Ω
      B25-4 (E2) - B39-79 (O1B-) Always Below 1 Ω
      Standard Resistance (Check for short)
      Tester Connection Condition Specified Condition
      B25-1 (HT1B) or B39-63 (HT1B) - Body ground Always 10 kΩ or higher
      B25-3 (OX1B) or B39-80 (OX1B) - Body ground Always 10 kΩ or higher
      B25-4 (E2) or B39-79 (O1B-) - Body ground Always 10 kΩ or higher

    4. Reconnect the heated oxygen sensor connector.

    5. Reconnect the ECM connector.

      A005RJYE36

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR (HEATED OXYGEN SENSOR - ECM)

    OK

  12. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor Click here.


    NEXT

  13. PERFORM CONFIRMATION DRIVING PATTERN

    Tech Tips

    Refer to the Confirmation Driving Pattern.


    NEXT

  14. CHECK WHETHER DTC OUTPUT RECURS (DTC P0136, P0137 OR P0138)


    1. Connect an intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

    5. Input DTCs: P0136, P0137 or P0138.

    6. Check that DTC MONITOR is NORMAL. If DTC MONITOR is INCOMPLETE, perform the drive pattern adding the vehicle speed.

      Result
      Display (DTC Output) Proceed to

      NORMAL

      (No DTC output)

      		 A

      ABNORMAL

      (P0136, P0137 or P0138 detected)

      		 B

    B

    REPLACE AIR FUEL RATIO SENSOR Click here

    A

    END

  15. REPLACE AIR FUEL RATIO SENSOR


    1. Replace the air fuel ratio sensor Click here.


    NEXT

  16. PERFORM CONFIRMATION DRIVING PATTERN

    Tech Tips

    Refer to the Confirmation Driving Pattern.


    NEXT

  17. CHECK WHETHER DTC OUTPUT RECURS (DTC P0136 OR P0138)


    1. Connect an intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester on.

    4. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

    5. Input DTCs: P0136 or P0138.

    6. Check that DTC MONITOR is NORMAL. If DTC MONITOR is INCOMPLETE, perform the drive pattern adding the vehicle speed.

      Result
      Display (DTC Output) Proceed to

      NORMAL

      (No DTC output)

      		 A

      ABNORMAL

      (P0136 or P0138 detected)

      		 B

    B

    REPLACE HEATED OXYGEN SENSOR Click here

    A

    END