SFI SYSTEM, Diagnostic DTC:P0137, P0157

DTC Code DTC Name
P0137 Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)
P0157 Oxygen Sensor Circuit Low Voltage (Bank 2 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. higher 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.

B003OCWE01
DTC No. Detection Item DTC Detection Condition Trouble Area MIL Memory
P0137 Oxygen Sensor Circuit Low Voltage (Bank 1 Sensor 2)

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 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

 Comes on DTC stored
P0157 Oxygen Sensor Circuit Low Voltage (Bank 2 Sensor 2)

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 rich.

  • Heated oxygen sensor (bank 2 sensor 2) circuit

  • Heated oxygen sensor (bank 2 sensor 2)

  • Air fuel ratio sensor (bank 2 sensor 1)

  • Gas leak from exhaust system

 Comes on DTC stored

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 (TWC) and heated oxygen sensor malfunctions (refer to the diagram below).

    Active air fuel ratio control is performed for approximately 30 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. Open or Short in Heated Oxygen Sensor Circuit (DTC P0137 and P0157)

    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 circuit, or the voltage output of the sensor noticeably decreases, the OSC indicates 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 or P0157.

    Tech Tips

    *: The TWC has the capability to store oxygen. The OSC and the emission purification capacity of the TWC are mutually related.

    B003O7LE02

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

Heated Oxygen Sensor Voltage Check (Low Voltage)
Active air fuel ratio control Executing
Active air fuel ratio control begins when all of the following conditions met: -
Battery voltage 11 V or higher
Engine coolant temperature 75°C (167°F) or higher
Idling Off
Engine speed Less than 3200 rpm
Air fuel ratio sensor status Activated
Fuel system status Closed loop
Engine load 10% or higher, and less than 80%

TYPICAL MALFUNCTION THRESHOLDS

P0137, P0157: Heated Oxygen Sensor Voltage Check (Low Voltage)
Both of the following conditions are met -
(a) Commanded air fuel ratio 14.3 or less
(b) Heated oxygen sensor voltage Less than 0.21 V

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.

B003QEJE37

  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).

  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 60 to 100 km/h (37 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 / Trouble Codes [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: P0137 or P0157.

  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 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

B003KPHE02

CAUTION / NOTICE / HINT

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 sensor, heated oxygen 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 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 and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / All Data / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.

  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 or AFS Voltage B2S1 and O2S B2S2) displayed on the GTS.

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 12.5%.

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

GTS Display

(Sensor)

 Injection Volume Status Voltage

AFS Voltage B1S1

AFS Voltage B2S1

(Air fuel ratio)

 12.5% Rich Below 3.1 V
-12.5% Lean Higher than 3.4 V

O2S B1S2

O2S B2S2

(Heated oxygen)

 12.5% Rich Higher than 0.55 V
-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.

B003JTXE20

Note

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

Tech Tips


  • Bank 1 refers to the bank that includes the No. 1 cylinder*.

    *: The No. 1 cylinder is the cylinder which is farthest from the transmission.

  • Bank 2 refers to the bank that does not include the No. 1 cylinder.

  • 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. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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 P0137 or P0157)


    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 and ECT / Trouble Codes.

    5. Read the DTCs.


      Powertrain > Engine > Trouble Codes
      Result
      Result Proceed to
      DTC P0137 or P0157 is output A
      DTC P0137 or P0157 and other DTCs are output B

      Tech Tips

      If any DTCs other than P0137 or P0157 are output, troubleshoot those DTCs first.


    B

    GO TO DTC CHART Click here

    A

  2. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

      Tech Tips

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

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT

    OK

  3. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)


    1. Inspect the heated oxygen sensor.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

  4. 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
      C98-1 (HT1B) - C82-18 (HT1B) Always Below 1 Ω
      C98-3 (OX1B) - C84-9 (OX1B) Always Below 1 Ω
      C98-4 (E2) - C84-10 (EX1B) Always Below 1 Ω
      C97-1 (HT2B) - C82-13 (HT2B) Always Below 1 Ω
      C97-3 (OX2B) - C84-3 (OX2B) Always Below 1 Ω
      C97-4 (E2) - C84-4 (EX2B) Always Below 1 Ω
      C98-1 (HT1B) or C82-18 (HT1B) - Body ground and other terminals Always 10 kΩ or higher
      C98-3 (OX1B) or C84-9 (OX1B) - Body ground and other terminals Always 10 kΩ or higher
      C97-1 (HT2B) or C82-13 (HT2B) - Body ground and other terminals Always 10 kΩ or higher
      C97-3 (OX2B) or C84-3 (OX2B) - Body ground and other terminals Always 10 kΩ or higher
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  5. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  6. PERFORM CONFIRMATION DRIVING PATTERN


    1. Perform the Confirmation Driving Pattern.

      Result
      Proceed to
      NEXT

    NEXT

  7. CHECK WHETHER DTC OUTPUT RECURS (DTC P0137 OR P0157)


    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 and ECT / Utility / All Readiness.


      Powertrain > Engine > Utility
      Tester Display
      All Readiness

    5. Input the DTC: P0137 or P0157.

    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

      NORMAL

      (DTCs are not output)

      		 A

      ABNORMAL

      (DTC P0137 or P0157 is output)

      		 B

      Tech Tips

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

      Click here


    A

    END

    B

    REPLACE AIR FUEL RATIO SENSOR Click here