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

CAUTION / NOTICE / HINT

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.

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 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 (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 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 or 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 (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 or P0157. 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 or P0158.

   *: 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.

   

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

CONFIRMATION DRIVING PATTERN

1. Connect the intelligent tester to the DLC3.

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

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

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

5. Turn the engine switch on (IG) 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 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 / 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 / Utility / All Readiness.

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

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

INSPECTION PROCEDURE

• 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 / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2; then press the view button.

PROCEDURE

1. READ OUTPUT DTC (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 / DTC.

   5. 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
      DTC P0136, P0137, P0138, P0156, P0157 or P0158 and other DTCs are output	D

      Tech Tips

      If any DTCs other than P0136, P0137, P0138, P0156, P0157 and P0158 are output, troubleshoot those DTCs first.

   
   

   B

   CHECK FOR EXHAUST GAS LEAK Click here

   C

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

   D

   GO TO DTC CHART 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).

   3. Turn the tester on.

   4. Enter the following menus: Powertrain / Engine / Data List / All Data / O2S B1S2 or O2S B2S2.

   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
      Less than 1.0 V	B

   
   

   B

   PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME) 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
      Tester Connection Condition Specified Condition 2 (+B) - 4 (E2) Always 10 kΩ or higher 2 (+B) - 3 (OX1B) Always 10 kΩ or higher 2 (+B) - 4 (E2) Always 10 kΩ or higher 2 (+B) - 3 (OX2B) Always 10 kΩ or higher

      Text in Illustration

      *1	Bank 1	*2	Bank 2
      *a	Component without harness connected (Heated Oxygen Sensor)	-	-

   
   

   NG

   REPLACE HEATED OXYGEN SENSOR Click here

   OK

4. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)

   
   

   1. Turn the engine switch to 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 E26-28 (HT1B) - E26-101 (OX1B) Always 10 kΩ or higher E26-22 (HT2B) - E26-133 (OX2B) Always 10 kΩ or higher

   
   

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

   REPLACE ECM Click here

5. 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 / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.

   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 fine graduations within the range.

      • The air fuel ratio sensor is displayed as AFS Voltage B1S1 or AFS Voltage B2S1, and the heated oxygen sensor is displayed as O2S B1S2 or O2S B2S2, 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 AFS Voltage B2S1 (Air fuel ratio)	Alternates between higher and less than 3.3 V	OK
      	Remains at higher than 3.3 V	NG
      	Remains at less than 3.3 V	NG

      Tech Tips

      A normal heated oxygen sensor voltage (O2S B1S2 or O2S B2S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor voltage (AFS Voltage B1S1 or AFS Voltage B2S1) remains at either less or higher 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

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 less than 2.2 mA in this test.

   
   

   1. Connect the intelligent tester to the DLC3.

   2. Start the engine.

   3. Turn the tester on.

   4. Clear the DTCs Click here.

   5. Drive the vehicle by the driving pattern as listed below:

      CAUTION:

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

      
      

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

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

      3. Stop the vehicle.

      4. Accelerate the vehicle to 60 km/h (37 mph) or more and decelerate for 5 seconds or more. Perform this 3 times.

         

   6. Enter the following menus: Powertrain / Engine / Data List / All Data / AFS Current B1S1 and AFS Current B2S1.

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

      Standard current
      Less than 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

   REPLACE HEATED OXYGEN SENSOR Click here

   NG

   REPLACE AIR FUEL RATIO SENSOR Click here

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 / Active Test / Control the Injection Volume / All Data / O2S B1S2 or O2S B2S2.

   6. Change the fuel injection volume using the tester, monitoring 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

   CHECK FOR EXHAUST GAS LEAK Click here

   OK

8. 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 / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.

   6. 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 fine graduations within the range.

      • The air fuel ratio sensor is displayed as AFS Voltage B1S1 or AFS Voltage B2S1, and the heated oxygen sensor is displayed as O2S B1S2 or O2S B2S2, 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 AFS Voltage B2S1 (Air fuel ratio)	Alternates between higher and less than 3.3 V	OK
      	Remains at higher than 3.3 V	NG
      	Remains at less than 3.3 V	NG

      Tech Tips

      A normal heated oxygen sensor voltage (O2S B1S2 or O2S B2S2) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor voltage (AFS Voltage B1S1 or AFS Voltage B2S1) remains at either less or higher 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 (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.

      Tech Tips

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

   
   

   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 E22-1 (HT1B) - E26-28 (HT1B) Always Below 1 Ω E22-3 (OX1B) - E26-101 (OX1B) Always Below 1 Ω E22-4 (E2) - E26-102 (EX1B) Always Below 1 Ω E20-1 (HT2B) - E26-22 (HT2B) Always Below 1 Ω E20-3 (OX2B) - E26-133 (OX2B) Always Below 1 Ω E20-4 (E2) - E26-134 (EX2B) Always Below 1 Ω E22-1 (HT1B) or E26-28 (HT1B) - Body ground Always 10 kΩ or higher E22-3 (OX1B) or E26-101 (OX1B) - Body ground Always 10 kΩ or higher E20-1 (HT2B) or E26-22 (HT2B) - Body ground Always 10 kΩ or higher E20-3 (OX2B) or E26-133 (OX2B) - 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, 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 the DTC: P0136, P0137, P0138, P0156, P0157 or P0158.

    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, P0138, P0156, P0157 or P0158 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

    END

    A

    REPLACE AIR FUEL RATIO SENSOR Click here

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, P0138, P0156 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 the DTC: P0136, P0138, P0156 or P0158.

    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, P0138, P0156 or P0158 is output)	A
       NORMAL (DTC is not output)	B

    
    

    B

    END

    A

    REPLACE HEATED OXYGEN SENSOR Click here