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 sensor, sends pre-catalyst information to the ECM. The second sensor, the heated oxygen sensor, sends post-catalyst information to the ECM.

In order to detect any deterioration in the three-way catalytic converter, the ECM calculates the oxygen storage capacity of the three-way catalytic converter. This calculation is based on the voltage output of the heated oxygen sensor while performing active air fuel ratio control.

The oxygen storage capacity value is an indication of the oxygen storage capacity of the three-way catalytic converter. 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 cycle of the waveform for the heated oxygen sensor is long, the oxygen storage capacity is great. There is a direct correlation between the heated oxygen sensor and the oxygen storage capacity of the three-way catalytic converter.

The ECM uses the oxygen storage capacity value to determine the state of the three-way catalytic converter. If any deterioration has occurred, the ECM illuminates the MIL and stores the DTC.

This system determines the deterioration of the entire catalyst system (including the front and rear catalysts), by using the oxygen storage capacity value of the front catalyst, that is more sensitive than the rear catalyst, as the representative value. Therefore, be sure to replace the front and rear catalysts together when catalyst replacement is necessary.

DTC No. DTC Detection Condition Trouble Area
P0420 The oxygen storage capacity 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 sensor (bank 1 sensor 1)

  • Heated oxygen sensor (bank 1 sensor 2)

  • Exhaust manifold sub-assembly RH (TWC: Front catalyst) and front exhaust pipe assembly (TWC: Rear catalyst)
P0430 The oxygen storage capacity 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 sensor (bank 2 sensor 1)

  • Heated oxygen sensor (bank 2 sensor 2)

  • Exhaust manifold sub-assembly LH (TWC: Front catalyst) and front exhaust pipe assembly (TWC: Rear catalyst)

CATALYST LOCATION

A01ETK5E01
Text in Illustration
*1 Air Fuel Ratio Sensor (Bank 1 Sensor 1) *2 Air Fuel Ratio Sensor (Bank 2 Sensor 1)
*3 Heated Oxygen Sensor (Bank 1 Sensor 2) *4 Heated Oxygen Sensor (Bank 2 Sensor 2)
*5 TWC: Front Catalyst *6 TWC: Rear Catalyst
*7 Center Exhaust Pipe Assembly *8 Tail Exhaust Pipe Assembly RH
*9 Tail Exhaust Pipe Assembly LH *10 Exhaust Manifold Sub-assembly RH
*11 Exhaust Manifold Sub-assembly LH *12 Front Exhaust Pipe Assembly

Note


  • When outputting DTC P0420 replace the exhaust manifold sub-assembly RH (*10) and the front exhaust pipe assembly (*12) together when catalyst replacement is necessary (Excluding air fuel ratio sensor *1 and heated oxygen sensor *3).

  • When outputting DTC P0430 replace the exhaust manifold sub-assembly LH (*11) and the front exhaust pipe assembly (*12) together when catalyst replacement is necessary (Excluding air fuel ratio sensor *2 and heated oxygen sensor *4).

MONITOR STRATEGY

Required Sensors/Components (Main)

Air fuel ratio sensor

Heated oxygen sensor
Required Sensors/Components (Related)

Intake air temperature sensor

Mass air flow meter sub-assembly

Crankshaft position sensor

Engine coolant temperature sensor
Frequency of Operation Once per driving cycle

TYPICAL ENABLING CONDITIONS

Battery voltage 11 V or higher
Intake air temperature -10°C (14°F) or higher
Engine coolant temperature 75°C (167°F) or higher
Atmospheric pressure 76 kPa(abs) [570 mmHg(abs)] or higher
Idling Off
Engine speed Less than 3200 rpm
Air fuel ratio sensor status Activated
Fuel system status Closed loop
Engine load 10% or higher, and less than 70%
All of the following conditions are met 1, 2 and 3
1. Mass air flow 5 gm/sec or more, and less than 75 gm/sec
2. Front catalyst temperature (estimated) 520°C (968°F) or higher, and less than 800°C (1472°F)
3. Rear catalyst temperature (estimated) 300°C (572°F) or higher, and less than 800°C (1472°F)
Shift position 3rd or higher

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.

A01EVN2E75

  1. Connect the intelligent tester to the DLC3.

  2. Turn the engine switch on (IG).

  3. Turn the tester on.

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

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

  10. 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.

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

  12. Input the DTC: P0420 or P0430.

  13. 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] and [E].

  14. Drive the vehicle at a speed between 75 and 100 km/h (47 and 62 mph) for 10 minutes or more [D].

    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.

  15. 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 air fuel ratio and heated oxygen sensors. This is to activate the sensors sufficiently to obtain appropriate inspection results.

A01EW8FE93

Tech Tips


  • If the voltage output of either the air fuel ratio or heated oxygen 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 Control the Injection Volume Active Test using the intelligent tester.

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

A01EXNWE18

INSPECTION PROCEDURE

Tech Tips


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

    *: The No. 1 cylinder is the cylinder which is farthest from the transaxle.

  • 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.

  • Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. 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).

    3. Turn the tester on.

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

    5. Read the DTCs.

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

      Tech Tips

      If any DTCs other than P0420 and/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 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 / Active Test / Control the Injection Volume / All Data / AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.

    6. Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).

    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% to +12%. The injection volume can be changed in fine gradations.

      • 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

      AFS Voltage B2S1

      (Air fuel ratio)

      		 +12% Rich Below 3.1 V
      -12% Lean Higher than 3.4 V

      O2S B1S2

      O2S B2S2

      (Heated oxygen)

      		 +12% Rich Higher than 0.55 V
      -12% 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

      		 Misfire 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 May occur

      • 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 correctly.


    B

    REPLACE AIR FUEL RATIO SENSOR Click here

    C

    CHECK FOR EXHAUST GAS LEAK Click here

    D

    CHECK FOR EXHAUST GAS LEAK Click here

    A

  3. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

    OK

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

    Note


    • When outputting DTC P0420 replace the exhaust manifold sub-assembly RH (TWC: Front catalyst) and the front exhaust pipe assembly (TWC: Rear catalyst) together when catalyst replacement is necessary.

    • When outputting DTC P0430 replace the exhaust manifold sub-assembly LH (TWC: Front catalyst) and the front exhaust pipe assembly (TWC: Rear catalyst) together when catalyst replacement is necessary.

    Tech Tips

    Confirm the replacement parts, referring to the illustration in the Catalyst Location.


    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 P0420 is output A, C
      DTC P0430 is output B, C
      DTC P0420 and P0430 are output A, B, C

    A

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

    B

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

    C

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

  5. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    OK

    REPLACE HEATED OXYGEN SENSOR Click here

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

  6. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    OK

    CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO Click here

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

  7. 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

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  8. REPAIR OR REPLACE EXHAUST GAS LEAK POINT


    1. Repair or replace exhaust gas leak point.

      Tech Tips

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


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  9. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor Click here.


    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED Click here

  10. 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

  11. 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 and wait for at least 30 seconds.

    6. Start the engine.

    7. Turn the tester on.

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

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

    10. Read the DTCs.

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

    B

    END

    A

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

    Note


    • When outputting DTC P0420 replace the exhaust manifold sub-assembly RH (TWC: Front catalyst) and the front exhaust pipe assembly (TWC: Rear catalyst) together when catalyst replacement is necessary.

    • When outputting DTC P0430 replace the exhaust manifold sub-assembly LH (TWC: Front catalyst) and the front exhaust pipe assembly (TWC: Rear catalyst) together when catalyst replacement is necessary.

    Tech Tips

    Confirm the replacement parts, referring to the illustration in the Catalyst Location.


    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 P0420 is output A, C
      DTC P0430 is output B, C
      DTC P0420 and P0430 are output A, B, C

    A

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

    B

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

    C

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