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)

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, rather than the conventional detecting method, which uses the locus ratio.

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 a 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 sets a DTC.

DTC No. DTC Detection Condition Trouble Area
P0420 OSC value smaller than standard value under active air-fuel ratio control (2 trip detection logic)

  • Gas leakage from exhaust system

  • A/F sensor (bank 1 sensor 1)

  • HO2 sensor (bank 1 sensor 2)

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

  • Front exhaust pipe assembly (TWC: Rear catalyst)
P0430 OSC value smaller than standard value under active air-fuel ratio control (2 trip detection logic)

  • Gas leakage from exhaust system

  • A/F sensor (bank 2 sensor 1)

  • HO2 sensor (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 No. 1 cylinder.

  • Bank 2 refers to the bank that does not include 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

A001F44E03

CONFIRMATION DRIVING PATTERN

Tech Tips

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

A001FHWE98

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

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

  8. Drive the vehicle at approximately 60 km/h (37 mph) for 10 minutes or more [B].

    CAUTION:

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

    Tech Tips

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

  9. Turn the engine switch off and wait for at least 30 seconds [C].

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

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

  12. Drive the vehicle at approximately 60 km/h (37 mph) for 10 minutes or more [E].

    CAUTION:

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

    Tech Tips

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

  13. Enter the following menus: Powertrain / Engine / DTC [F].

  14. Check if any DTCs (pending DTCs) are stored.

    Tech Tips


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

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

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

    CAUTION:

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

    Tech Tips

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

  16. Enter the following menus: Powertrain / Engine / DTC [H].

  17. Input the DTC: P0420 or P0430.

  18. 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.

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.

A001BD5E14

  • (a) Connect the intelligent tester to the DLC3.

  • (b) Start the engine and warm it up with all the accessories switched OFF, until the engine coolant temperature stabilizes.

  • (c) Run the engine at an engine speed of between 2500 rpm and 3000 rpm for at least 3 minutes.

  • (d) While running the engine at 3000 rpm for 2 seconds and 2000 rpm for 2 seconds, check the waveforms of the A/F and HO2 sensors using the tester.

Tech Tips


  • If either of the voltage outputs of the Air-Fuel Ratio (A/F) or Heated Oxygen (HO2) sensor does not fluctuate, or either of the sensors makes a noise, 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 menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.

  • 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).

A001DE6E01

CAUTION / NOTICE / HINT

Tech Tips


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

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 / DTC.

    4. Read the DTCs.

      Result
      Display (DTC Output) Proceed to
      P0420 and/or P0430 A
      P0420 and/or P0430 and other DTCs B

      Tech Tips

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


    B

    GO TO DTC CHART Click here

    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 turn the tester ON.

    3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

    4. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.

    5. Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

    6. Monitor the voltage outputs of the A/F and HO2 sensors (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

        (A/F)

        		 +12.5% Rich Less than 3.1

        AFS voltage B1S1 or AFS voltage B2S1

        (A/F)

        		 -12.5% Lean More than 3.4

        O2S B1S2 or O2S B2S2

        (HO2)

        		 +12.5% Rich More than 0.55

        O2S B1S2 or O2S B2S2

        (HO2)

        		 -12.5% Lean Less than 0.4
        Result

        Status

        AFS voltage B1S1

        or

        AFS voltage B2S1

        Status

        O2S B1S2

        or

        O2S B2S2

        A/F Condition and A/F and

        HO2 Sensors Conditions

        		 Misfires Main Suspected Trouble Area Proceed to
        Lean/Rich Lean/Rich Normal -

        • Three-Way Catalytic Converter (TWC)

        • Gas leakage from exhaust system

        		 A
        Lean Lean/Rich A/F sensor malfunction -

        • A/F sensor

        		 B
        Rich Lean/Rich A/F sensor malfunction -

        • A/F sensor
        Lean/Rich Lean HO2 sensor malfunction -

        • HO2 sensor

        • Gas leakage from exhaust system

        		 C
        Lean/Rich Rich HO2 sensor malfunction -

        • HO2 sensor

        • Gas leakage from exhaust system
        Lean Lean Actual air-fuel ratio lean May occur

        • Extremely rich or lean actual air-fuel ratio

        • Gas leakage from exhaust system

        		 A
        Rich Rich Actual air-fuel ratio rich -

        • Extremely rich or lean actual air-fuel ratio

        • Gas leakage from exhaust system

        Lean: During Control the Injection Volume for A/F Sensor, the A/F sensor output voltage (AFS) is consistently more than 3.4 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.

        Rich: During Control the Injection Volume for A/F Sensor, the AFS is consistently less than 3.1 V, and the O2S is consistently more than 0.55 V.

        Lean/Rich: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the HO2 sensor alternates correctly.


    B

    CHECK AND REPLACE AIR FUEL RATIO SENSOR Click here

    C

    CHECK AND REPLACE HEATED OXYGEN SENSOR, AND CHECK AND REPAIR EXHAUST GAS LEAKAGE Click here

    A

  3. CHECK FOR EXHAUST GAS LEAK

    OK
    No gas leakage.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

    OK

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


    1. According to the DTCs output in step 1 (Check Any Other DTCs Output), proceed to the next step referring to the table below.

      Result
      Display (DTC output) Proceed to
      P0420 (2WD) A, E
      P0420 (AWD) B, E
      P0430 (2WD) C, E
      P0430 (AWD) D, E
      P0420 and P0430 (2WD) A, C, E
      P0420 and P0430 (AWD) B, D, E

    E

    REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST) Click here

    A

    REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY LH (FOR 2WD) (TWC: FRONT CATALYST) Click here

    B

    REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY LH (FOR AWD) (TWC: FRONT CATALYST) Click here

    C

    REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY RH (FOR 2WD) (TWC: FRONT CATALYST) Click here

    D

    REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY RH (FOR AWD) (TWC: FRONT CATALYST) Click here