SFI SYSTEM, Diagnostic DTC:P0136, P0137, P0138, P0139

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.

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 (HO2) 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 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 DTCs P0136.

   

3. Open in Heated Oxygen (HO2) Sensor Circuit (DTC P0137)

   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.

   Tech Tips

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

   

4. High or Low Impedance of Heated Oxygen (HO2) Sensor (DTCs P0136 or P0137)

   During normal air fuel ratio feedback control, there are small variations in the exhaust gas oxygen concentration. In order to continuously monitor the slight variation of the heated oxygen sensor signal while the engine is running, the impedance* of the sensor is measured by the ECM. The ECM determines that there is a malfunction in the sensor when the measured impedance deviates from the standard range.

   

   *: The effective resistance in an alternating current electrical circuit.

   Tech Tips

   • The impedance cannot be measured using an ohmmeter.

   • DTC P0136 indicates the deterioration of the heated oxygen sensor. The ECM stores the DTC by calculating the impedance of the sensor when the typical enabling conditions are satisfied (2 driving cycles).

   • DTC P0137 indicates an open or short circuit in the heated oxygen sensor (2 driving cycles). The ECM stores the DTC when the impedance of the sensor exceeds the threshold 15 kΩ.

5. Extremely High Output Voltage of Heated Oxygen (HO2) Sensor (DTC P0138)

   The ECM continuously monitors the heated oxygen sensor output voltage while the engine is running.

   DTC P0138 is stored if the heated oxygen sensor voltage output is 1.2 V or higher for 10 seconds or more.

6. Abnormal Voltage Output of Heated Oxygen (HO2) Sensor During Fuel-cut (DTC P0139)

   The sensor output voltage drops to below 0.2 V (extremely lean status) immediately when the vehicle decelerates and fuel cut is operating. If the voltage does not drop to below 0.2 V for 7 seconds or more, or voltage does not drop from 0.35 V to 0.2 V for 1 second or more, the ECM determines that the sensor response has deteriorated, illuminates the MIL and stores a DTC.

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

MONITOR RESULT

Refer to detailed information in Checking Monitor Status Click here.

CONFIRMATION DRIVING PATTERN

P0136, P0137 and P0138

1. Connect the Techstream to the DLC3.

2. Turn the ignition switch to ON and turn the Techstream 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 Techstream 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 75 to 120 km/h (47 to 75 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: P0136, P0137 or P0138.

12. Check the DTC judgment result.

    Techstream 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.

13. If no pending DTC is output, perform a universal trip and check for permanent DTCs Click here.

    Tech Tips

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

    • If no permanent DTC is output, the system is normal.

P0139

1. Connect the Techstream to the DLC3.

2. Turn the ignition switch to ON and turn the Techstream 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 Techstream 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 S position, drive the vehicle at 60 km/h (37 mph), and then decelerate the vehicle by releasing the accelerator pedal for 5 seconds or more to perform the fuel-cut [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 DTCs.

   Tech Tips

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

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

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

11. Input the DTC: P0139.

12. Check the DTC judgment result.

    Techstream 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, drive the vehicle with the shift lever in S position, and then perform steps [C] and [D] again.

13. If no pending DTC is output, perform a universal trip and check for permanent DTCs Click here.

    Tech Tips

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

    • If no permanent DTC is output, the system is normal.

WIRING DIAGRAM

Refer to DTC P0037 Click here.

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 and ECT / Active Test / Control the Injection Volume / Gas AF Control / AFS Voltage B1S1 and O2S B1S2; and then press the graph button on the Data List view.

PROCEDURE

1. READ OUTPUT DTC (DTC P0136, P0137, P0138 OR P0139)

   1. Connect the Techstream to the DLC3.

   2. Turn the ignition switch to ON.

   3. Turn the Techstream on.

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

   5. Read the DTCs.

      Result

      Result	Proceed to
      P0138 is output	A
      P0137 is output	B
      P0136 is output	C
      P0139 is output	D
      P0136, P0137 or P0138 and other DTCs are output	E

      Tech Tips

      If any DTCs other than P0136, P0137, P0138 or P0139 are output, troubleshoot those DTCs first.

   B

   CHECK FOR EXHAUST GAS LEAK Click here

   C

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

   D

   CHECK FOR EXHAUST GAS LEAK Click here

   E

   GO TO DTC CHART Click here

   A

2. 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

      Text in Illustration

      *a	Component without harness connected (Heated Oxygen Sensor)

   NG

   REPLACE HEATED OXYGEN SENSOR Click here

   OK

3. CHECK HARNESS AND CONNECTOR (CHECK FOR SHORT)

   1. Turn the ignition 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 E26-24 (HT1B) - E26-100 (OX1B) Always 10 kΩ or higher

   NG

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

   REPLACE ECM Click here

4. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME)

   1. Connect the Techstream to the DLC3.

   2. Start the engine.

   3. Turn the Techstream on.

   4. Warm up the engine.

   5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / Gas AF Control / O2S B1S2.

   6. Change the fuel injection volume using the Techstream, and monitor the voltage output of heated oxygen sensor displayed on the Techstream.

      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

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

   1. Connect the Techstream to the DLC3.

   2. Turn the ignition switch to ON.

   3. Turn the Techstream on.

   4. Warm up the engine.

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

   6. Change the fuel injection volume using the Techstream, and monitor the voltage output of air fuel ratio and heated oxygen sensors displayed on the Techstream.

      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 Techstream.

      • 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

      Techstream Display (Sensor)	Voltage Variation	Proceed to
      AFS Voltage B1S1 (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) reacts in accordance with increases and decreases in fuel injection volumes. When the air fuel ratio sensor voltage (AFS Voltage B1S1) 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

6. 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

7. INSPECT HEATED OXYGEN SENSOR (HEATER RESISTANCE)

   1. Inspect the heated oxygen sensor Click here.

   NG

   REPLACE HEATED OXYGEN SENSOR Click here

   OK

8. 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

   REPAIR OR REPLACE HARNESS OR CONNECTOR

   OK

9. REPLACE HEATED OXYGEN SENSOR

   1. Replace the heated oxygen sensor Click here.

   NEXT

10. PERFORM CONFIRMATION DRIVING PATTERN

    1. Perform the Confirmation Driving Pattern (P0136, P0137 and P0138).

    NEXT

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

    1. Connect the Techstream to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the Techstream on.

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

    5. Input DTCs: P0136, P0137 or P0138.

    6. Check that the DTC monitor is NORMAL. If the DTC monitor is INCOMPLETE, perform the drive 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

    END

    A

    REPLACE AIR FUEL RATIO SENSOR Click here

12. 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

13. PERFORM CONFIRMATION DRIVING PATTERN

    1. Perform the Confirmation Driving Pattern (P0136, P0137 and P0138).

    NEXT

14. CHECK WHETHER DTC OUTPUT RECURS (DTC P0136)

    1. Connect the Techstream to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the Techstream on.

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

    5. Input DTCs: P0136.

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

       Result

       Result	Proceed to
       NORMAL (DTC is not output)	A
       ABNORMAL (DTC P0136 is output)	B

    B

    REPLACE HEATED OXYGEN SENSOR Click here

    A

    END

15. 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

16. INSPECT HEATED OXYGEN SENSOR (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

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

17. PERFORM CONFIRMATION DRIVING PATTERN

    1. Perform the Confirmation Driving Pattern (P0139).

    NEXT

18. READ OUTPUT DTC (DTC P0139 IS OUTPUT AGAIN)

    1. Connect the Techstream to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the Techstream on.

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

    5. Input DTCs: P0139.

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

       Result

       Result	Proceed to
       ABNORMAL (DTC P0139 is output)	A
       NORMAL (DTC is not output)	B

    B

    CHECK FOR INTERMITTENT PROBLEMS Click here

    A

    REPLACE HEATED OXYGEN SENSOR Click here