SFI SYSTEM, Diagnostic DTC:P0420, P0430

DTC Code DTC Name
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0430 Catalyst System Efficiency Below Threshold (Bank 2)

MONITOR DESCRIPTION

The ECM uses sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency.

The first sensor, the Air-Fuel Ratio (A/F) sensor, sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor, sends post-catalyst information to the ECM.

In order to detect any deterioration in the TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the HO2 sensor while performing active air-fuel ratio control.

The OSC value is an indication of the oxygen storage capacity of the TWC. When the vehicle is being driven with a warm engine, active air-fuel ratio control is performed for approximately 15 to 20 seconds. When it is performed, the ECM deliberately sets the air-fuel ratio to lean or rich levels. If the rich-lean cycle of the HO2 sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the HO2 sensor and the TWC.

The ECM uses the OSC value to determine the state of the TWC. If any deterioration has occurred, it illuminates the MIL and stores the DTC.

DTC Code DTC Detection Condition Trouble Area
P0420 The OSC value is less than the standard value under active air-fuel ratio control (2 trip detection logic).
  • Gas leak from exhaust system

  • Air-Fuel Ratio (A/F) sensor (for Bank 1 Sensor 1)

  • Heated Oxygen (HO2) sensor (for Bank 1 Sensor 2)

  • Exhaust manifold sub-assembly LH (TWC: Front Catalyst)

  • Front No. 2 exhaust pipe assembly (TWC: Rear Catalyst)

P0430 The OSC value is less than the standard value under active air-fuel ratio control (2 trip detection logic).
  • Gas leak from exhaust system

  • Air-Fuel Ratio (A/F) sensor (for Bank 2 Sensor 1)

  • Heated Oxygen (HO2) sensor (for Bank 2 Sensor 2)

  • Exhaust manifold sub-assembly RH (TWC: Front Catalyst)

  • Front exhaust pipe assembly (TWC: Rear Catalyst)

Tech Tips


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

  • 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.

CATALYST LOCATION

B001AHXE02

CONFIRMATION DRIVING PATTERN

Tech Tips

Performing this confirmation driving pattern will activate the catalyst monitor. This is very useful for verifying the completion of a repair.

B001AQRE06

  1. Connect the intelligent tester to the DLC3.

  2. Turn the engine switch on (IG).

  3. Turn the tester on.

  4. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).

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

  6. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher [A].

  7. Drive the vehicle at approximately 60 km/h (38 mph) for 10 minutes or more [B].

    Tech Tips

    Drive the vehicle while keeping the engine load as constant as possible.

    CAUTION:

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

  8. Enter the following menus: Powertrain / Engine and ECT / DTC [C].

  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: P0420 or P0430.

  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 [D] through [E].

  13. Drive the vehicle at a speed between 75 and 100 km/h (47 and 63 mph) for 10 minutes or more [D].

    Tech Tips

    Drive the vehicle while keeping the engine load as constant as possible.

    CAUTION:

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

  14. Check the DTC judgment result again [E].

CONDITIONING FOR SENSOR TESTING

Tech Tips

Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.

B0018XWE01

Tech Tips


  • If either voltage output of the Air-Fuel Ratio (A/F) or Heated Oxygen (HO2) sensor does not fluctuate, or there is a noise in the waveform of either sensor, the sensor may be malfunctioning.

  • If the voltage outputs of both the sensors remain lean or rich, the air-fuel ratio may be extremely lean or rich. In such cases, perform the following Control the Injection Volume for A/F Sensor using the intelligent tester.

  • If the Three-Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).

B0019E3E40

CAUTION / NOTICE / HINT

Tech Tips


  • If a malfunction cannot be found when troubleshooting DTC P0420, P0430 a lean or rich abnormality may be the cause. Perform troubleshooting by following the inspection procedure for P0171, P0174 (System Too Lean) and P0172, P0175 (System Too Rich).

  • 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.

  • 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.

PROCEDURE


  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 AND/OR P0430)


    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 and ECT / DTC.

    4. Read DTCs.

      Result
      Result Proceed to
      P0420 or P0430 is output A
      P0420 or P0430 and other DTCs are output B

      Tech Tips

      If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.


    B
    A
  2. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and warm it up.

    3. Turn the tester on.

    4. 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.

    6. Perform the Control the Injection Volume operation with the engine idling.

    7. Monitor the voltage outputs of the air fuel ratio sensor and heated oxygen sensor (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the tester.

      Tech Tips


      • Change the fuel injection volume within the range of - 12.5% to +12.5%.

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

      • 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.

      Standard

      Tester Display

      (Sensor)

      Injection Volume Status Voltage

      AFS Voltage B1S1 or AFS Voltage B2S1

      (Air fuel ratio)

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

      O2S B1S2 or O2S B2S2

      (Heated oxygen)

      +12.5% Rich Higher than 0.55 V
      -12.5% Lean Below 0.4 V
      Result

      Status

      AFS Voltage B1S1 or AFS Voltage B2S1

      Status

      O2S B1S2 or O2S B2S2

      Actual air fuel ratio, air fuel ratio sensor and

      heated oxygen sensor condition

      Main Suspected Trouble Area Proceed to
      Lean/Rich Lean/Rich Normal
      • Three-way catalytic converter

      • Gas leak from exhaust system

      A
      Lean Lean/Rich Air fuel ratio sensor malfunction
      • Air fuel ratio sensor

      B
      Rich Lean/Rich Air fuel ratio sensor malfunction
      • Air fuel ratio sensor

      Lean/Rich Lean Heated oxygen sensor malfunction
      • Heated oxygen sensor

      • Gas leak from exhaust system

      C
      Lean/Rich Rich Heated oxygen sensor malfunction
      • Heated oxygen sensor

      • Gas leak from exhaust system

      Lean Lean Actual air fuel ratio lean
      • Extremely rich or lean actual air fuel ratio

      • Gas leak from exhaust system

      D
      Rich Rich Actual air fuel ratio rich
      • Extremely rich or lean actual air fuel ratio

      • Gas leak from exhaust system

      Lean: During Control the Injection Volume, the air fuel ratio sensor output voltage (AFS Voltage B1S1 or AFS Voltage B2S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2 or O2S B2S2) is consistently below 0.4 V.

      Rich: During Control the Injection Volume, the AFS Voltage B1S1 or AFS Voltage B2S1 is consistently below 3.1 V, and the O2S B1S2 or O2S B2S2 is consistently higher than 0.55 V.

      Lean/Rich: During Control the Injection Volume of the Active Test, the output voltage of the air fuel ratio sensor and heated oxygen sensor alternate


    B
    C
    D
    A
  3. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    NG
    OK
  4. CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)


    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 and ECT / DTC.

    5. Read the DTCs.

      Result
      Result Proceed to
      P0420 A, B
      P0430 C, D
      P0420 and P0430 A, B, C and D

    A
    B
    C
    D
  5. REPLACE AIR FUEL RATIO SENSOR


    1. Replace the air fuel ratio sensor Click here.


    NEXT
  6. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    NG
    OK
  7. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor Click here.


    NEXT
  8. CHECK EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    NG
    OK
  9. CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR-FUEL RATIO


    1. Check the cause of extremely rich or lean actual air fuel ratio, referring to the DTC P0171 Inspection Procedure Click here.


    NEXT
  10. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED


    1. Connect the intelligent tester to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the tester on.

    4. Clear the DTCs Click here.

    5. Turn the engine switch off.

    6. Start the engine and warm it up.

    7. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

    8. Enter the following menus: Powertrain / Engine and ECT / DTC.

    9. Read the DTCs.

      Result
      Result Proceed to
      DTC P0420 or P0430 is output A
      DTC is not output B

    B
    A
  11. CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)


    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 and ECT / DTC.

    5. Read the DTCs.

      Result
      Result Proceed to
      P0420 A, B
      P0430 C, D
      P0420 and P0430 A, B, C and D

    A
    B
    C
    D