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

In order to obtain a high purification rate of the carbon monoxide (CO), hydrocarbon (HC) and nitrogen oxide (NOx) components in the exhaust gas, a TWC (Three-Way Catalytic Converter) is used. For the most efficient use of the TWC, the air fuel ratio must be precisely controlled so that it is always close to the stoichiometric air fuel level. 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 TWC, 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 high. The heated oxygen sensor informs the ECM that the post-TWC 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 is low. The heated oxygen sensor informs the ECM that the post-TWC 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 TWC is rich or lean, and adjusts the fuel injection duration 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.

A01EJ4PE09
DTC No. DTC Detection Condition Trouble Area
P0136

  • Abnormal voltage output:

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


    • (a) Heated oxygen sensor voltage does not increase to 0.69 V or higher.


    • (b) Heated oxygen sensor voltage does not decrease to less than 0.21 V.

  • Heated oxygen sensor (bank 1 sensor 2) circuit

  • Heated oxygen sensor (bank 1 sensor 2)

  • Air fuel ratio sensor (bank 1 sensor 1)

  • Gas leak from exhaust system

  • Fuel pressure

  • Fuel injector assembly

  • PCV valve and hose

  • Intake system
P0137

  • Low voltage (open):

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


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


    • (b) Target air fuel ratio is rich.

  • Heated oxygen sensor (bank 1 sensor 2) circuit

  • Heated oxygen sensor (bank 1 sensor 2)

  • Air fuel ratio sensor (bank 1 sensor 1)

  • Gas leak from exhaust system
P0138

  • High voltage (short):

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


    • (a) Heated oxygen sensor voltage output is higher than 0.69 V.


    • (b) Target air fuel ratio is lean.

  • Heated oxygen sensor (bank 1 sensor 2) circuit

  • Heated oxygen sensor (bank 1 sensor 2)

  • Air fuel ratio sensor (bank 1 sensor 1)

  • ECM

MONITOR DESCRIPTION


  1. Active Air Fuel Ratio Control

    The ECM usually performs air fuel ratio feedback control so that the air fuel ratio sensor output indicates a near stoichiometric air fuel level. This vehicle includes active air fuel ratio control in addition to regular air fuel ratio control. The ECM performs active air fuel ratio control to detect any deterioration in the three-way catalytic converter and heated oxygen sensor malfunctions (refer to the diagram below).

    Active air fuel ratio control is performed for approximately 15 to 20 seconds while driving with a warm engine. During active air fuel ratio control, the air fuel ratio is forcibly regulated to become lean or rich by the ECM. If the ECM detects a malfunction, a DTC is stored.

  2. Abnormal Voltage Output of Heated Oxygen Sensor (DTC P0136)

    While the ECM is performing active air fuel ratio control, the air fuel ratio is forcibly regulated to become rich or lean. If the sensor is not functioning properly, the voltage output variation is small. For example, when the heated oxygen sensor voltage does not decease to less than 0.21 V and does not increase to 0.69 V or higher during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormal and stores DTC P0136.

    A01EIORE19

  3. Open or Short in Heated Oxygen Sensor Circuit (DTC P0137 or P0138)

    During active air fuel ratio control, the ECM calculates the Oxygen Storage Capacity (OSC)* of the Three-Way Catalytic Converter (TWC) by forcibly regulating the air fuel ratio to become rich or lean. If the heated oxygen sensor has an open or short circuit, or the voltage output of the sensor noticeably decreases, the OSC indicated an extraordinarily high value. Even if the ECM attempts to continue regulating the air fuel ratio to become rich or lean, the heated oxygen sensor output does not change.

    While performing active air fuel ratio control, when the target air fuel ratio is rich and the heated oxygen sensor voltage output is less than 0.21 V (lean), the ECM interprets this as an abnormally low sensor output voltage and stores DTC P0137. When the target air fuel ratio is lean and the voltage output is higher than 0.69 V (rich) during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormally high and stores DTC P0138.

    *: The TWC has the capability to store oxygen. The OSC and the emissions purification capacity of the TWC are mutually related. The ECM determines whether the catalyst has deteriorated based on the calculated OSC value Click here.

    A01EJ0ME42

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 driving pattern will activate the heated oxygen sensor monitor (the catalyst monitor is performed simultaneously). This is very useful for verifying the completion of a repair.

A01EIMYE29

  1. Connect the GTS to the DLC3.

  2. Turn the ignition switch to ON and turn the GTS on.

  3. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) Click here.

  4. Turn the ignition switch off and wait for at least 30 seconds.

  5. Turn the ignition switch to ON and turn the GTS on [A].

  6. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher [B].

  7. With the shift lever in D, drive the vehicle at 43 to 62 mph (70 to 100 km/h) for 10 minutes or more [C].

    CAUTION:

    When performing the confirmation driving pattern, obey all speed limits and traffic laws.

  8. Enter the following menus: Powertrain / Engine / Trouble Codes.

  9. Read the pending DTCs [D].

    Tech Tips


    • If a pending DTC is output, the system is malfunctioning.

    • If a pending DTC is not output, perform the following procedure.

  10. Enter the following menus: Powertrain / Engine / Utility / All Readiness.

  11. Input the DTC: P0136, P0137 or P0138.

  12. Check the DTC judgment result.

    GTS Display Description
    NORMAL

    • DTC judgment completed

    • System normal
    ABNORMAL

    • DTC judgment completed

    • System abnormal
    INCOMPLETE

    • DTC judgment not completed

    • Perform driving pattern after confirming DTC enabling conditions
    N/A

    • Unable to perform DTC judgment

    • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit

    Tech Tips


    • If the judgment result shows ABNORMAL, the system has a malfunction.

    • If the judgment result shows NORMAL, the system is normal.

    • If the judgment result shows INCOMPLETE or N/A, perform steps [C] and [D] again.

WIRING DIAGRAM

A01ELE8E01

INSPECTION PROCEDURE

Tech Tips

Malfunctioning areas can be identified by performing the Control the Injection Volume function provided in the Active Test. The Control the Injection Volume function can help to determine whether the air fuel ratio sensor, heated oxygen sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume operation using the GTS.


  1. Connect the GTS to the DLC3.

  2. Start the engine.

  3. Turn the GTS on.

  4. Warm up the engine and run the engine at an engine speed of 2500 rpm for approximately 90 seconds.

  5. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2.

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

  7. Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the GTS.

Tech Tips


  • Change the fuel injection volume within the range of -12% to 12%. The injection volume can be changed in fine gradations.

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

GTS Display (Sensor) Injection Volume Status Voltage

AFS Voltage B1S1

(Air fuel ratio)

 12% Rich Below 3.1 V
-12% Lean Higher than 3.4 V

O2S B1S2

(Heated oxygen)

 12% Rich Higher than 0.55 V
-12% 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 Air Fuel Ratio Sensor (Sensor 1) Output Voltage Heated Oxygen Sensor (Sensor 2) Output Voltage Main Suspected Trouble Area
1 A01ELH1E05 A01EMMZE08 A01ELH1E05 A01ELHYE06 -
2 A01ELH1E05 A01EKK9E01 A01ELH1E05 A01ELHYE06

  • Air fuel ratio sensor

  • Air fuel ratio sensor heater

  • Air fuel ratio sensor circuit
3 A01ELH1E05 A01EMMZE08 A01ELH1E05 A01EKK9E01

  • Heated oxygen sensor

  • Heated oxygen sensor heater

  • Heated oxygen sensor circuit
4 A01ELH1E05 A01EKK9E01 A01ELH1E05 A01EKK9E01

  • Fuel injector assembly

  • 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


  • Sensor 1 refers to the sensor closest to the engine assembly.

  • Sensor 2 refers to the sensor farthest away from the engine assembly.

  • Read freeze frame data using the GTS. 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 the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Enter the following menus: Powertrain / Engine / Trouble Codes.

    5. Read the DTCs.

      Result
      Result Proceed to
      DTC P0138 is output A
      DTC P0137 is output B
      DTC P0136 is output C
      DTC P0136, P0137 or P0138 and other DTCs are output D

      Tech Tips

      If any DTCs other than P0136, P0137 and P0138 are output, troubleshoot those DTCs first.


    B

    CHECK FOR EXHAUST GAS LEAK Click here

    C

    PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME) Click here

    D

    GO TO DTC CHART Click here

    A

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


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine.

    5. Enter the following menus: Powertrain / Engine / Data List / All Data / O2S B1S2.

    6. Allow the engine to idle.

    7. 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 GTS (CONTROL THE INJECTION VOLUME) Click here

    A

  3. INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)

    A01EJR3E04
    Text in Illustration
    *a

    Component without harness connected

    (Heated Oxygen Sensor)

    1. 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

    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

  4. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)


    1. Turn the ignition switch off and wait for 5 minutes or more.

    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
      B58-41 (HT1B) - B58-125 (OX1B) Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

    REPLACE ECM Click here

  5. PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine.

    5. Warm up the engine.

    6. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2.

    7. Change the fuel injection volume using the GTS and monitor the voltage output of the air fuel ratio sensor and heated oxygen sensor displayed on the GTS.

      Tech Tips


      • Change the fuel injection volume within the range of -12% to 12%. The injection volume can be changed in fine gradations.

      • The air fuel ratio sensor is displayed as AFS Voltage B1S1, and the heated oxygen sensor is displayed as O2S B1S2 on the GTS.

      • 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.

      • If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

      Result
      GTS Display (Sensor) Voltage Variation Proceed to
      AFS Voltage B1S1 (Air fuel ratio) Alternates between higher than and less than 3.3 V OK
      Remains higher than 3.3 V NG
      Remains at less than 3.3 V NG

      Tech Tips

      A normal heated oxygen sensor voltage (O2S B1S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor voltage (AFS Voltage B1S1) remains either less or higher than 3.3 V despite the heated oxygen sensor indicating a normal reaction, the air fuel ratio sensor is malfunctioning.

      A01ELXPE59

    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 2.2 mA in this test.


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Clear the DTCs Click here.

    5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

    6. Drive the vehicle at 37 mph (60 km/h) or more for 10 minutes or more.

      CAUTION:

      When performing the confirmation driving pattern, obey all speed limits and traffic laws.

    7. Stop the vehicle.

    8. Enter the following menus: Powertrain / Engine / Data List / All Data / AFS Current B1S1.

    9. Drive the vehicle at 37 mph (60 km/h) or more and decelerate the vehicle for 5 seconds or more. Perform this 3 times.

      CAUTION:

      When performing the confirmation driving pattern, obey all speed limits and traffic laws.

      A01EKQUE53

    10. Read the value of the air fuel ratio sensor current while the fuel-cut operation is being performed.

      Standard current
      Below 2.2 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 GTS.


    OK

    REPLACE HEATED OXYGEN SENSOR Click here

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

  7. PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME)


    1. Connect the GTS to the DLC3.

    2. Start the engine.

    3. Turn the GTS on.

    4. Warm up the engine.

    5. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume / All Data / O2S B1S2.

    6. Change the fuel injection volume using the GTS and monitor the voltage output of the heated oxygen sensors displayed on the GTS.

      Tech Tips


      • Change the fuel injection volume within the range of -12% to 12%. The injection volume can be changed in fine gradations.

      • The heated oxygen sensor has a maximum output delay of approximately 20 seconds.

      Standard Voltage
      Fluctuates between 0.4 V or less and 0.55 V or higher.

    NG

    CHECK FOR EXHAUST GAS LEAK Click here

    OK

  8. PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Start the engine.

    5. Warm up the engine.

    6. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2.

    7. Change the fuel injection volume using the GTS and monitor the voltage output of the air fuel ratio and heated oxygen sensors displayed on the GTS.

      Tech Tips


      • Change the fuel injection volume within the range of -12% to 12%. The injection volume can be changed in fine gradations.

      • The air fuel ratio sensor is displayed as AFS Voltage B1S1, and the heated oxygen sensor is displayed as O2S B1S2 on the GTS.

      • 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.

      • If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

      Result
      GTS Display (Sensor) Voltage Variation Proceed to
      AFS Voltage B1S1 (Air fuel ratio) Alternates between higher than and below 3.3 V OK
      Remains higher than 3.3 V NG
      Remains below 3.3 V NG

      Tech Tips

      A normal heated oxygen sensor voltage (O2S B1S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor voltage (AFS Voltage B1S1) remains either less or higher than 3.3 V despite the heated oxygen sensor indicating a normal reaction, the air fuel ratio sensor is malfunctioning.

      A01ELXPE59

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

    OK

    CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO (FUEL INJECTOR ASSEMBLY, FUEL SYSTEM, INTAKE SYSTEM, ETC.) Click here

  9. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT

    OK

  10. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)


    1. Inspect the heated oxygen sensor Click here.


    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

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


    1. 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
      Tester Connection Condition Specified Condition
      B57-1 (HT1B) - B58-41 (HT1B) Always Below 1 Ω
      B57-3 (OX1B) - B58-125 (OX1B) Always Below 1 Ω
      B57-4 (E2) - B58-102 (O1B-) Always Below 1 Ω
      B57-1 (HT1B) or B58-41 (HT1B) - Body ground Always 10 kΩ or higher
      B57-3 (OX1B) or B58-125 (OX1B) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  12. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor Click here.


    NEXT

  13. PERFORM CONFIRMATION DRIVING PATTERN


    1. Perform Confirmation Driving Pattern.


    NEXT

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


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

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

    5. Input the DTC: P0136, P0137 or P0138.

    6. Check that the DTC monitor is NORMAL. If the DTC monitor is INCOMPLETE, perform the driving pattern again but increase the vehicle speed.

      Result
      Result Proceed to

      ABNORMAL

      (DTC P0136, P0137 or P0138 is output)

      		 A

      NORMAL

      (DTC is not output)

      		 B

    B

    END

    A

    REPLACE AIR FUEL RATIO SENSOR Click here

  15. REPLACE AIR FUEL RATIO SENSOR


    1. Replace the air fuel ratio sensor Click here.


    NEXT

  16. PERFORM CONFIRMATION DRIVING PATTERN


    1. Perform Confirmation Driving Pattern.


    NEXT

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


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

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

    5. Input the DTC: P0136 or P0138.

    6. Check that the DTC monitor is NORMAL. If the DTC monitor is INCOMPLETE, perform the driving pattern again but increase the vehicle speed.

      Result
      Result Proceed to

      ABNORMAL

      (DTC P0136 or P0138 is output)

      		 A

      NORMAL

      (DTC is not output)

      		 B

    B

    END

    A

    REPLACE HEATED OXYGEN SENSOR Click here