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 leaks from exhaust system

  • Air fuel ratio sensor (bank 1 sensor 1)

  • Heated oxygen 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 leaks from exhaust system

  • Air fuel ratio sensor (bank 2 sensor 1)

  • Heated oxygen 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

A0160IAE02

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.

A015YSQE03

  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 (38 mph) for 10 minutes or more [B].

    Tech Tips

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

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

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

    Tech Tips

    If the monitor does not change to Complete, and no pending DTCs are stored, perform the following procedure.

  11. 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.

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

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

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.

A016125E59

  • (a) Connect the intelligent tester to the DLC3 [A].

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

  • (c) Run the engine at an engine speed of between 1000 rpm and 2000 rpm for at least 3 minutes [C].

  • (d) While running the engine at 2000 rpm for 2 seconds and 1000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the tester [D].

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 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 / Active Test / Control the Injection Volume for A/F Sensor.

  • If the three way catalytic converter has deteriorated, the heated oxygen sensor (located behind the three way catalytic converter) voltage output fluctuates up and down frequently, even under normal driving conditions (active air fuel ratio control is not performed).

A015ZNAE04

INSPECTION PROCEDURE

Tech Tips

Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the Air-Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using the intelligent tester.


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

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

  6. Monitor the output voltages 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


  • 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.

Tester Display (Sensor) Injection Volume Status Voltage

AFS Voltage B1S1 or AFS Voltage B2S1

(A/F)

 +25% Rich Less than 3.1 V

AFS Voltage B1S1 or AFS Voltage B2S1

(A/F)

 -12.5% Lean More than 3.4 V

O2S B1S2 or O2S B2S2

(HO2)

 +25% Rich More than 0.55 V

O2S B1S2 or O2S B2S2

(HO2)

 -12.5% Lean Less than 0.4 V

Note

The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.

Case A/F Sensor (Sensor 1) Output Voltage HO2 Sensor (Sensor 2) Output Voltage Main Suspected Trouble Area
1 A0162ADE01 A0160FEE04 A0162ADE01 A0161P9E01 -
2 A0162ADE01 A015ZP2E01 A0162ADE01 A0161P9E01

  • A/F sensor

  • A/F sensor heater

  • A/F sensor circuit
3 A0162ADE01 A0160FEE04 A0162ADE01 A015ZP2E01

  • HO2 sensor

  • HO2 sensor heater

  • HO2 sensor circuit
4 A0162ADE01 A015ZP2E01 A0162ADE01 A015ZP2E01

  • Injector

  • Fuel pressure

  • Gas leaks from exhaust system (Air-fuel ratio extremely rich or lean)

Tech Tips

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 be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

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 (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 / Data List / AFS Voltage B1S1, AFS Voltage B2S1, O2S B1S2 and O2S B2S2.

    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


      • 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

        (A/F)

        		 +25% Rich Less than 3.1 V

        AFS Voltage B1S1 or AFS Voltage B2S1

        (A/F)

        		 -12.5% Lean More than 3.4 V

        O2S B1S2 or O2S B2S2

        (HO2)

        		 +25% Rich More than 0.55 V

        O2S B1S2 or O2S B2S2

        (HO2)

        		 -12.5% Lean Less than 0.4 V
        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 leaks 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 leaks from exhaust system

        		 C
        Lean/Rich Rich HO2 sensor malfunction -

        • HO2 sensor

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

        • Extremely lean actual air-fuel ratio

        • Gas leaks from exhaust system

        		 D
        Rich Rich Actual air-fuel ratio rich -

        • Extremely rich actual air-fuel ratio

        • Gas leaks 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

    REPLACE AIR FUEL RATIO SENSOR Click here

    C

    INSPECT FOR EXHAUST GAS LEAK Click here

    D

    INSPECT FOR EXHAUST GAS LEAK 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. 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 DTCs.

      Result
      Display (DTC Output) Proceed to
      P0420 A
      P0430 B
      P0420 and P0430 A and B

    B

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

    A

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


    1. Replace the exhaust manifold sub-assembly LH (TWC: front catalyst) Click here.


    NEXT

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

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


    1. Replace the exhaust manifold sub-assembly RH (TWC: front catalyst) Click here.


    NEXT

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

  7. INSPECT FOR EXHAUST GAS LEAK

    OK
    No gas leaks.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT

    OK

    REPLACE HEATED OXYGEN SENSOR Click here

  8. INSPECT FOR EXHAUST GAS LEAK

    OK
    No gas leaks.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT

    OK

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