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.

A01EV96E22
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 0.59 V or higher.


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


  • Heated oxygen sensor (sensor 2) circuit

  • Heated oxygen sensor (sensor 2)

  • Air fuel ratio sensor (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 (sensor 2) circuit

  • Heated oxygen sensor (sensor 2)

  • Air fuel ratio sensor (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 0.59 V.


    • (b) Target air fuel ratio is lean.


  • Heated oxygen sensor (sensor 2) circuit

  • Heated oxygen sensor (sensor 2)

  • Air fuel ratio sensor (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 (A/F) 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 (TWC) and Heated Oxygen (HO2) 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 decrease to less than 0.21 V and does not increase to 0.59 V or higher during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormal and stores DTC P0136.

    A01EVTFE36
  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 0.59 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.

    A01EW7AE30

MONITOR STRATEGY

Required Sensors/Components (Main) Heated oxygen sensor (sensor 2)
Required Sensors/Components (Related)

Crankshaft position sensor

Engine coolant temperature sensor

Mass air flow meter sub-assembly

Throttle position sensor

Air fuel ratio sensor

Frequency of Operation Once per driving cycle

TYPICAL ENABLING CONDITIONS

P0136, P0137 and P0138: Heated Oxygen Sensor Voltage Check (Voltage Malfunction, High Voltage and Low Voltage)
Active air fuel ratio control Executing
Active air fuel ratio control begins when all of following conditions met: -
Battery voltage 11 V or higher
Engine coolant temperature 75°C (167°F) or higher
Idling OFF
Engine speed Less than 4000 rpm
Air fuel ratio sensor status Activated
Fuel system status Closed loop
Engine load 10 to 80%

TYPICAL MALFUNCTION THRESHOLDS

P0136: Heated Oxygen Sensor Voltage Check (Voltage Malfunction)
Either of following conditions met: 1 or 2
1. Both of following conditions met (a) and (b)
(a) Commanded air fuel ratio 14.4 or less
(b) Heated oxygen sensor voltage 0.21 V or higher, and less than 0.59 V
2. Both of following conditions met (c) and (d)
(c) Commanded air fuel ratio 14.8 or more
(d) Heated oxygen sensor voltage 0.21 V or higher, and less than 0.59 V
P0137: Heated Oxygen Sensor Voltage Check (Low Voltage)
Both of following conditions met (a) and (b)
(a) Commanded air fuel ratio 14.4 or less
(b) Heated oxygen sensor voltage Less than 0.21 V
P0138: Heated Oxygen Sensor Voltage Check (High Voltage)
Both of following conditions met (a) and (b)
(a) Commanded air fuel ratio 14.8 or more
(b) Heated oxygen sensor voltage Higher than 0.59 V

CONFIRMATION DRIVING PATTERN

A01EZ4YE96

  1. Connect the intelligent tester to the DLC3.

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

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

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

  5. Turn the ignition switch to ON and turn the tester 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 70 to 100 km/h (43 to 62 mph) 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 and ECT / DTC [D].

  9. Read the pending DTCs.

    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 and ECT / Utility / All Readiness.

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

  12. Check the DTC judgment result.

    Tester 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 NORMAL, the system is normal.

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

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

WIRING DIAGRAM

Refer to DTC P0037 Click here.

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 intelligent tester.


  1. Connect the intelligent tester to the DLC3.

  2. Start the engine and turn the tester on.

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

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

  5. Perform the Active Test operation with the engine idling.

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

Tech Tips


  • Change the fuel injection volume within the range of -12.0% to +12.0%. The injection volume can be changed in fine gradations.

  • 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.

Tester Display (Sensor) Injection Volume Status Voltage

AFS Voltage B1S1

(Air fuel ratio)

+12% Rich Below 3.1 V

AFS Voltage B1S1

(Air fuel ratio)

-12% Lean Higher than 3.4 V

O2S B1S2

(Heated oxygen)

+12% Rich Higher than 0.55 V

O2S B1S2

(Heated oxygen)

-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 A01EXYBE05 A01EWKXE08 A01EXYBE05 A01EWEDE06 -
2 A01EXYBE05 A01EUBZE01 A01EXYBE05 A01EWEDE06
  • Air fuel ratio sensor

  • Air fuel ratio sensor heater

  • Air fuel ratio sensor circuit

3 A01EXYBE05 A01EWKXE08 A01EXYBE05 A01EUBZE01
  • Heated oxygen sensor

  • Heated oxygen sensor heater

  • Heated oxygen sensor circuit

4 A01EXYBE05 A01EUBZE01 A01EXYBE05 A01EUBZE01
  • Fuel injector assembly

  • Fuel pressure

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

Tech Tips


  • Following the Control the Injection Volume procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.

  • To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2; and then press the graph button on the Data List view.

  • 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 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 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.

    5. Read 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
    C
    D
    A
  2. 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 / 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
    A
  3. INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)

    A01EX27E99
    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
    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
      E26-24 (HT1B) - E26-100 (OX1B) Always 10 kΩ or higher

    NG
    OK
  5. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME)


    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. Warm up the engine.

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

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

      Tech Tips


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

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

      • 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
      Tester 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 (AFS Voltage B1S1) voltage 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.

      A01EVFFE27

    NG
    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. When the sensor is normal, the sensor current will indicate below 2.2 mA in this test.


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the tester 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 60 km/h (37 mph) 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 and ECT / Data List / All Data / AFS Current B1S1.

    9. Drive the vehicle at 60 km/h (37 mph) 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.

      A01EVUSE43
    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 tester.


    OK
    NG
  7. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE 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 / All Data / O2S B1S2.

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

      Tech Tips


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

      • 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
    OK
  8. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME)


    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. Warm up the engine.

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

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

      Tech Tips


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

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

      • 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
      Tester 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 (AFS Voltage B1S1) voltage 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.

      A01EVFFE27

    NG
    OK
  9. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

      Tech Tips

      Perform "Inspection After Repair" after repairing or replacing the exhaust system Click here.


    NG
    OK
  10. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)


    1. Inspect the heated oxygen sensor Click here.


    NG
    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
      E21-1 (HT1B) - E26-24 (HT1B) Always Below 1 Ω
      E21-3 (OX1B) - E26-100 (OX1B) Always Below 1 Ω
      E21-4 (E2) - E26-132 (EX1B) Always Below 1 Ω
      E21-1 (HT1B) or E26-24 (HT1B) - Body ground Always 10 kΩ or higher
      E21-3 (OX1B) or E26-100 (OX1B) - Body ground Always 10 kΩ or higher

    NG
    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 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 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

      Tech Tips

      Perform "Inspection After Repair" after replacing the air fuel ratio sensor Click here.


    B
    A
  15. REPLACE AIR FUEL RATIO SENSOR


    1. Replace the air fuel ratio sensor Click here.

      Tech Tips

      Perform "Inspection After Repair" after replacing 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, P0137 OR P0138)


    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 / 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
    A