SFI SYSTEM, Diagnostic DTC:P0136, P0137, P0138, P0156, P0157, P0158

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 three-way catalytic converter is used. For the most efficient use of the three-way catalytic converter, 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 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.

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, one of the following DTCs is set: DTC P0136 or P0156 (abnormal voltage output), P0137 or P0157 (open circuit) or P0138 or P0158 (short circuit).

2. Abnormal Voltage Output of Heated Oxygen Sensor (DTCs P0136 and P0156)

   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 more than 0.59 V during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormal and sets DTCs P0136 and P0156.

   

3. Open or Short in Heated Oxygen Sensor Circuit (DTCs P0137 and P0157 or P0138 and P0158)

   During active air fuel ratio control, the ECM calculates the oxygen storage capacity (OSC)* of the three-way catalytic converter by forcibly regulating the air fuel ratio to become rich or lean.

   If the heated oxygen sensor has an open or short, or the voltage output of the sensor noticeably decreases, the oxygen storage capacity 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 0.21 V or less (lean), the ECM interprets this as an abnormally low sensor output voltage and sets DTC P0137 or P0157. When the target air fuel ratio is lean and the voltage output is 0.59 V or more (rich) during active air fuel ratio control, the ECM determines that the sensor voltage output is abnormally high, and sets DTC P0138 or P0158.

   Tech Tips

   DTC P0138 or P0158 is also set if the heated oxygen sensor voltage output is more than 1.2 V for 10 seconds or more.

   ^*: The three-way catalytic converter has the capability to store oxygen. The oxygen storage capacity and the emission purification capacity of the three-way catalytic converter are mutually related. The ECM determines whether the catalyst has deteriorated, based on the calculated oxygen storage capacity value Click here.

   

WIRING DIAGRAM

CONFIRMATION DRIVING PATTERN

1. Connect the intelligent tester to the DLC3.

2. Warm-up the engine until the engine coolant temperature is 75°C (167°F) or more [A].

3. Drive the vehicle at 80 to 128 km/h (50 to 80 mph) for at 10 minutes [B].

4. Drive the vehicle 60 km/h (40 mph) or more and decelerate the vehicle for 5 seconds or more. Perform this 3 times [C].

5. Turn the tester ON.

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

7. Input DTCs: P0136, P0137, P0138, P0156, P0157 and P0158.

8. Check that DTC MONITOR is NORMAL. If DTC MONITOR is INCOMPLETE, perform the drive pattern adding the vehicle speed and using the second gear to decelerate the vehicle.

INSPECTION PROCEDURE

• Following the Control the Injection Volume for A/F sensor 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 / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2.

PROCEDURE

1. READ DTC OUTPUT

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the engine switch on (IG) and turn the tester ON.

   3. Enter the following menus: Powertrain / Engine / DTC.

   4. Read the DTCs.

      Result
      Result Proceed to DTC P0138 or P0158 is output A DTC P0137 or P0157 is output B DTC P0136 or P0156 is output 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 the intelligent tester to the DLC3.

   2. Turn the engine switch on (IG) and turn the tester ON.

   3. Enter the following menus: Powertrain / Engine / Data List / A/F Control System / O2S B1 S2 or O2S B2 S2.

   4. Allow the engine to idle.

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

      Result
      Tester Display Result Proceed to O2S B1S2 or O2S B2S2 1.0 V or more A Less than 1.0 V B

   
   

   B

   CHECK AIR FUEL RATIO SENSOR Click here

   A

3. INSPECT HEATED OXYGEN SENSOR (CHECK FOR SHORT)

   
   

   1. 

      Disconnect the heated oxygen sensor connector.

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

      Standard Resistance (Bank 1 Sensor 2)
      Tester Connection Condition Specified Condition 2 (+B) - 4 (E2) Always 10 kΩ or higher 2 (+B) - 3 (OX1B)

      Standard Resistance (Bank 2 Sensor 2)
      Tester Connection Condition Specified Condition 2 (+B) - 4 (E2) Always 10 kΩ or higher 2 (+B) - 3 (OX2B)

   3. Reconnect the heated oxygen sensor connector.

   
   

   NG

   REPLACE HEATED OXYGEN SENSOR Click here

   OK

4. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)

   
   

   1. 

      Turn the engine 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 (Bank 1 Sensor 2)
      Tester Connection Condition Specified Condition A6-4 (HT1B) - A6-26 (OX1B) Always 10 kΩ or higher

      Standard Resistance (Bank 2 Sensor 2)
      Tester Connection Condition Specified Condition A6-3 (HT2B) - A6-27 (OX2B) Always 10 kΩ or higher

   4. Reconnect the ECM connector.

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

   REPLACE ECM Click here

5. CHECK 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 3 mA in this test.

   
   

   1. Clear the DTC Click here.

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

      
      

      1. Warm up the engine.

      2. Drive the vehicle at 60 km/h (40 mph) or more for 10 minutes or more.

      3. Stop the vehicle.

      4. Accelerate the vehicle until 60 km/h (40 mph) or more and decelerate for 5 seconds or more. Perform this three times.

         

   3. Enter the following menus: Powertrain / Engine / Data List / A/F Control System / AFS B1 S1 and AFS B2 S1.

   4. Read the value.

      Standard
      Less than 3.0 mA

      Note

      Do not turn the engine switch off during this step because the test results will be lost.

   
   

   NG

   REPLACE AIR FUEL RATIO SENSOR Click here

   OK

6. REPLACE HEATED OXYGEN SENSOR

   
   

   1. Replace the heated oxygen sensor Click here.

   
   

   NEXT

7. PERFORM CONFIRMATION DRIVING PATTERN

   Tech Tips

   Refer to Confirmation Driving Pattern.

   
   

   NEXT

8. CHECK WHETHER DTC OUTPUT RECURS (DTC P0136, P0137, P0138, P0156, P0157 OR P0158)

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the engine switch on (IG).

   3. Turn the tester ON.

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

   5. Input DTC: P0136, P0137, P0138, P0156, P0157 or P0158.

      Check the DTC MONITOR is NORMAL. If DTC MONITOR is INCOMPLETE, perform the drive pattern increasing the vehicle speed and using the second gear to decelerate the vehicle.

      Result
      Result Proceed to NORMAL A ABNORMAL B

   
   

   B

   REPLACE AIR FUEL RATIO SENSOR Click here

   A

   END

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

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Turn the engine switch on (IG) and turn the tester ON.

   3. Start the engine.

   4. Enter the following menus: Powertrain / Engine / Data List / A/F Control System / O2S B1 S2 or O2S B2 S2.

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

   6. Read the output voltage of the heated oxygen sensor when the engine rpm is suddenly increased.

      Tech Tips

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

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

   
   

   NG

   CHECK EXHAUST GAS LEAK Click here

   OK

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

    
    

    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and turn the tester ON.

    3. Warm up the engine.

    4. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume.

    5. Change the fuel injection volume using the tester, and monitor the voltage output of air fuel ratio and heated oxygen sensors 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 1% graduations within the range.

       • The air fuel ratio sensor is displayed as AFS B1 S1 or AFS B2 S1, and the heated oxygen sensor is displayed as O2S B1 S2 or O2S B2 S2 on the intelligent tester.

       Result
       Tester Display (Sensor) Voltage Variation Proceed to AFS B1 S1 (Air fuel ratio) AFS B2 S1 (Air fuel ratio) Alternates between more and less than 3.3 V OK AFS B1 S1 (Air fuel ratio) AFS B2 S1 (Air fuel ratio) Remains at more than 3.3 V NG AFS B1 S1 (Air fuel ratio) AFS B2 S1 (Air fuel ratio) Remains at less than 3.3 V NG

       Tech Tips

       A normal heated oxygen sensor voltage (O2S B1 S2 or O2S B2 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 3.3 V despite the heated oxygen sensor indicating a normal reaction, the air fuel ratio sensor is malfunctioning.

       

    
    

    NG

    REPLACE AIR FUEL RATIO SENSOR Click here

    OK

    CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO

11. CHECK EXHAUST GAS LEAK

    
    

    1. Check for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipes.

       OK
       No gas leaks.

    
    

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

    OK

12. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

    
    

    1. 

       Disconnect the heated oxygen sensor connector.

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

       Standard Resistance (Bank 1 Sensor 2)
       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

       Standard Resistance (Bank 2 Sensor 2)
       Tester Connection Condition Specified Condition 1 (HT2B) - 2 (+B) 20°C (68°F) 11 to 16 Ω 1 (HT2B) - 4 (E2) Always 10 kΩ or higher

    3. Reconnect the heated oxygen sensor connector.

    
    

    NG

    REPLACE HEATED OXYGEN SENSOR Click here

    OK

13. 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 (Check for Open)
       Bank 1
       Tester Connection Condition Specified Condition J68-1 (HT1B) - A6-4 (HT1B) Always Below 1 Ω J68-3 (OX1B) - A6-26 (OX1B) J68-4 (E2) - E3-28 (E2)
       Bank 2
       Tester Connection Condition Specified Condition J40-1 (HT2B) - A6-3 (HT2B) Always Below 1 Ω J40-3 (OX2B) - A6-27 (OX2B) J40-4 (E2) - E3-28 (E2)

       Standard Resistance (Check for Short)
       Bank 1
       Tester Connection Condition Specified Condition J68-1 (HT1B) or A6-4 (HT1B) - Body ground Always 10 kΩ or higher J68-3 (OX1B) or A6-26 (OX1B) - Body ground
       Bank 2
       Tester Connection Condition Specified Condition J40-1 (HT2B) or A6-3 (HT2B) - Body ground Always 10 kΩ or higher J40-3 (OX2B) or A6-27 (OX2B) - Body ground

    4. Reconnect the heated oxygen sensor connector.

    5. Reconnect the ECM connector.

    
    

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

14. REPLACE HEATED OXYGEN SENSOR

    
    

    1. Replace the heated oxygen sensor Click here.

    
    

    NEXT

15. PERFORM CONFIRMATION DRIVING PATTERN

    Tech Tips

    Refer to Confirmation Driving Pattern.

    
    

    NEXT

16. CHECK WHETHER DTC OUTPUT RECURS (DTC P0136, P0137, P0138, P0156, P0157 OR P0158)

    
    

    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the tester ON.

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

    5. Input DTC: P0136, P0137, P0138, P0156, P0157 or P0158.

       Check the DTC MONITOR is NORMAL. If DTC MONITOR is INCOMPLETE, perform the drive pattern increasing the vehicle speed and using the second gear to decelerate the vehicle.

       Result
       Result Proceed to NORMAL A ABNORMAL B

    
    

    B

    REPLACE AIR FUEL RATIO SENSOR Click here

    A

    END

17. REPLACE AIR FUEL RATIO SENSOR

    
    

    1. Replace the air fuel ratio sensor Click here.

    
    

    NEXT

18. PERFORM CONFIRMATION DRIVING PATTERN

    Tech Tips

    Refer to the Confirmation Driving Pattern.

    
    

    NEXT

19. CHECK WHETHER DTC OUTPUT RECURS (DTC P0136, P0137, P0138, P0156, P0157 OR P0158)

    
    

    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the tester ON.

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

    5. Input DTC: P0136, P0137, P0138, P0156, P0157 or P0158.

       Check the DTC MONITOR is NORMAL. If DTC MONITOR is INCOMPLETE, perform the drive pattern increasing the vehicle speed and using the second gear to decelerate the vehicle.

       Result
       Result Proceed to NORMAL A ABNORMAL B

    
    

    B

    REPLACE HEATED OXYGEN SENSOR Click here

    A

    END