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 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 TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the heated oxygen 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 a rich-lean cycle of the heated oxygen sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the heated oxygen sensor and 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 a DTC.

DTC No. DTC Detection Condition Trouble Area
P0420 Oxygen storage capacity value is smaller than the standard value under active air fuel ratio control (2 trip detection logic).

  • Gas leakage 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)

  • Front exhaust pipe assembly (TWC: Rear Catalyst)
P0430 Oxygen storage capacity value is smaller than the standard value under active air fuel ratio control (2 trip detection logic).

  • Gas leakage 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)

  • Front No. 2 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

A00O4ZLE02
Text in Illustration
*1 Exhaust Manifold Sub-Assembly RH (TWC: Front Catalyst) *2 Exhaust Manifold Sub-Assembly LH (TWC: Front Catalyst)
*3 Front Exhaust Pipe (TWC: Rear Catalyst) *4 Front No. 2 Exhaust Pipe (TWC: Rear Catalyst)
*5 Center Exhaust Pipe Assembly *6 Tailpipe Assembly
*7 Air Fuel Ratio Sensor (for Bank 1 Sensor 1) *8 Air Fuel Ratio Sensor (for Bank 2 Sensor 1)
*9 Heated Oxygen Sensor (for Bank 1 Sensor 2) *10 Heated Oxygen Sensor (for Bank 2 Sensor 2)

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.

A00O6QPE78

  1. Connect the intelligent tester to the DLC3.

  2. Turn the ignition switch to ON.

  3. Turn the intelligent tester on.

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

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

  6. Turn the ignition switch to ON and turn the intelligent tester on.

  7. Enter the following menus: Powertrain / Engine and ECT / Monitor.

  8. Check that Catalyst / Status2 is Incomplete.

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

  10. Drive the vehicle between 40 and 70 mph (64 and 113 km/h) for 10 minutes or more [B].

  11. The monitor items will change to Complete as the catalyst monitor operates.

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

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

Tech Tips

If Catalyst does not change to Complete, and no pending DTCs are stored, extend the driving time.

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 in order to activate the sensors sufficiently to obtain the appropriate inspection results.

A00O5YFE99

  • (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 then 2000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the intelligent tester.

Tech Tips


  • If either of the voltage outputs of the air fuel ratio or heated oxygen sensor does not fluctuate, or either of the sensors makes a noise, the sensor may be malfunctioning.

  • If the voltage outputs of both of the sensors remain lean or rich, the air-fuel ratio may be extremely lean or rich. In such cases, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.

  • If the Three-Way Catalytic Converter (TWC) has deteriorated, the heated oxygen 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).

A00OA5JE45

INSPECTION PROCEDURE

Tech Tips

Malfunctioning areas can be identified by performing the Control the Injection Volume for air fuel ratio sensor function provided in the Active Test. The Control the Injection Volume for air fuel ratio sensor function can help to determine whether the air fuel ratio sensor, heated oxygen sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for air fuel ratio sensor operation using the intelligent tester.


  1. Connect the intelligent tester to the DLC3.

  2. Start the engine and turn the intelligent tester on.

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

  4. On the intelligent tester, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

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

  6. Monitor the output voltages of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the intelligent tester.

Tech Tips


  • The Control the Injection Volume for air fuel ratio sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.

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

Tester Display (Sensor) Injection Volume Status Voltage

AFS Voltage B1S1 or AFS Voltage B2S1

(Air fuel ratio sensor)

 +25% Rich Below 3.1 V

AFS Voltage B1S1 or AFS Voltage B2S1

(Air fuel ratio sensor)

 -12.5% Lean Higher than 3.4 V

O2S B1S2 or O2S B2S2

(Heated oxygen sensor)

 +25% Rich Higher than 0.55 V

O2S B1S2 or O2S B2S2

(Heated oxygen sensor)

 -12.5% Lean Below 0.4 V

Note

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.

Case Air Fuel Ratio Sensor (Sensor 1) Output Voltage Heated Oxygen Sensor (Sensor 2) Output Voltage Main Suspected Trouble Area
1 A00O5STE01 A00O3R3E08 A00O5STE01 A00O30ZE04 -
2 A00O5STE01 A00O5QEE01 A00O5STE01 A00O30ZE04

  • Air fuel ratio sensor

  • Air fuel ratio sensor heater

  • Air fuel ratio sensor circuit
3 A00O5STE01 A00O3R3E08 A00O5STE01 A00O5QEE01

  • Heated oxygen sensor

  • Heated oxygen sensor heater

  • Heated oxygen sensor circuit
4 A00O5STE01 A00O5QEE01 A00O5STE01 A00O5QEE01

  • Fuel injector assembly

  • Fuel pressure

  • Gas leakage from exhaust system (air fuel ratio extremely rich or lean)

Tech Tips

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 FOR ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 AND/OR P0430)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch to ON and turn the intelligent tester on.

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

    4. Read DTCs.

      Result
      Result 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 FOR A/F SENSOR)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and turn the intelligent 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 and ECT / Active Test / Control the Injection Volume for A/F Sensor.

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

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

      Tech Tips


      • The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.

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

        Standard

        Tester Display

        (Sensor)

        		 Injection Volume Status Voltage

        AFS Voltage B1S1 or AFS Voltage B2S1

        (Air fuel ratio sensor)

        		 +25% Rich Below 3.1 V

        AFS Voltage B1S1 or AFS Voltage B2S1

        (Air fuel ratio sensor)

        		 -12.5% Lean Higher than 3.4 V

        O2S B1S2 or O2S B2S2

        (Heated oxygen sensor)

        		 +25% Rich Higher than 0.55 V

        O2S B1S2 or O2S B2S2

        (Heated oxygen sensor)

        		 -12.5% Lean Below 0.4 V
        Result

        Status of

        AFS Voltage B1S1

        or

        AFS Voltage B2S1

        Status of

        O2S B1S2

        or

        O2S B2S2

        		 Air Fuel Ratio Condition and 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 (TWC)

        • Gas leakage 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

        		 B
        Lean/Rich Lean Heated oxygen sensor malfunction -

        • Heated oxygen sensor

        • Gas leakage from exhaust system

        		 C
        Lean/Rich Rich Heated oxygen sensor malfunction -

        • Heated oxygen sensor

        • Gas leakage from exhaust system

        		 C
        Lean Lean Actual air-fuel ratio lean May occur

        • Extremely rich or lean actual air-fuel ratio

        • Gas leakage from exhaust system

        		 D
        Rich Rich Actual air-fuel ratio rich -

        • Extremely rich or lean actual air-fuel ratio

        • Gas leakage from exhaust system

        		 D

        Lean: During Control the Injection Volume for A/F Sensor, the air fuel ratio sensor output voltage (AFS) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently below 0.4 V.

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

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


    B

    REPLACE AIR FUEL RATIO SENSOR Click here

    C

    INSPECT EXHAUST FOR GAS LEAK Click here

    D

    CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR-FUEL RATIO, REPLACE FAULTY AREA AND GO TO NEXT STEP

    A

  3. INSPECT FOR EXHAUST GAS LEAK

    OK
    No gas leakage.
    Result
    Result Proceed to
    NG A
    OK B

    B

    CHECK DTC OUTPUT (DTC P0420 AND/OR P0430) Click here

    A

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT

  4. INSPECT EXHAUST FOR GAS LEAK

    OK
    No gas leakage.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

    OK

    REPLACE HEATED OXYGEN SENSOR Click here

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


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

      Result
      Result Proceed to
      P0420 A
      P0430 B
      P0420 and P0430 A and B

    B

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

    A

  6. REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY RH (TWC: FRONT CATALYST)


    1. Replace the exhaust manifold sub-assembly RH Click here.


    NEXT

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

  7. REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY LH (TWC: FRONT CATALYST)


    1. Replace the exhaust manifold sub-assembly LH Click here.


    NEXT

    REPLACE FRONT NO. 2 EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST) Click here