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SFI SYSTEM, Diagnostic DTC:P0420, P0430

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

The ECM uses the sensors mounted in front of and behind the three-way catalyst converter to monitor its efficiency. The first sensor, an air fuel ratio sensor, sends pre-catalyst air fuel ratio information to the ECM. The second sensor, a heated oxygen sensor (O2S), sends post-catalyst information to the ECM. The ECM compares these 2 signals to judge the efficiency of the catalyst and the catalyst's ability to store oxygen. During normal operation, the three-way catalyst converter stores and releases oxygen as needed. The capacity to store oxygen results in a low variation in the post-three-way catalyst converter exhaust stream.

If the catalyst is functioning normally, the waveform of the heated oxygen sensor slowly switches between RICH and LEAN. If the catalyst is deteriorated, the waveform will alternate frequently between RICH and LEAN. As the catalyst efficiency degrades, its ability to store oxygen is reduced and the catalyst output becomes more variable. When running the monitor, the ECM compares sensor 1 signals (air fuel ratio sensor) over a specific amount of time to determine catalyst efficiency. The ECM begins by calculating the signal length for both sensors (for the rear oxygen sensor, the ECM uses the output voltage signal length). If the oxygen sensor output voltage signal length is greater than the threshold (threshold is calculated based on the air fuel ratio sensor signal length), the ECM concludes that the catalyst is malfunctioning. The ECM will turn on the MIL and a DTC will be set.

DTC No. DTC Detection Condition Trouble Area
P0420 Oxygen Storage Capacity (OSC) value is smaller than 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)

  • Center exhaust pipe assembly (TWC: Rear catalyst)
P0430 OSC value is smaller than 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)

  • Center exhaust pipe assembly (TWC: Rear catalyst)
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CATALYST LOCATION

Table 1. Text in Illustration
*a

Exhaust Manifold Sub-assembly LH

(TWC: Front Catalyst)

 *b

Exhaust Manifold Sub-assembly RH

(TWC: Front Catalyst)
*c

Air Fuel Ratio Sensor

(Bank 2 Sensor 1)

 *d

Air Fuel Ratio Sensor

(Bank 1 Sensor 1)
*e Front Exhaust Pipe Assembly *f

Heated Oxygen Sensor

(Bank 2 Sensor 2)
*g Front No. 3 Exhaust Pipe Sub-assembly *h

Heated Oxygen Sensor

(Bank 1 Sensor 2)
*i

Center Exhaust Pipe Assembly

(TWC: Rear Catalyst)

 *j Tail Exhaust Pipe Assembly
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CONFIRMATION DRIVING PATTERN

Tip:

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


  1. Connect the intelligent tester to the DLC3.

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

  6. Turn the ignition 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].

    Tip:

    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.

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

  10. Read the pending DTCs.

    Tip:

    • 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 and ECT / 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
    UNKNOWN

    • Unable to perform DTC judgment

    • Number of DTCs which do not fulfill DTC preconditions has reached ECU memory limit
    Tip:

    • 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 UNKNOWN, perform steps [D] through [E].

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

    Tip:

    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.

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

A017EX0E08
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CONDITIONING FOR SENSOR TESTING

Tip:

Perform the operation with the engine speeds and 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.


  1. Connect the intelligent tester to the DLC3 (Proceed to "A").

  2. Start the engine and warm it up with all the accessories switched off, until the engine coolant temperature stabilizes (Procedure "B").

  3. Run the engine at an engine speed of between 2500 rpm and 3000 rpm for at least 3 minutes (Procedure "C").

  4. While running the engine at 3000 rpm for 2 seconds and at 2000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the tester (Procedure "D").

    Tip:

    • If either of the voltage outputs of the Control the Injection Volume for A/F 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 using the intelligent tester.

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

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INSPECTION PROCEDURE


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  1. AIR FUEL RATIO CONTROL

    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 sensor, heated oxygen 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 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. Enter the following menus: Powertrain / Engine and ECT / 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 air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the tester.

      Tip:

      • 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 voltage
      Tester Display Injection Volumes Status Voltages
      AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio) +25% Rich Less than 3.1 V
      AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio) -12.5% Lean More than 3.4 V
      O2S B1S2 or O2S B2S2 (Heated oxygen) +25% Rich More than 0.55 V
      O2S B1S2 or O2S B2S2 (Heated oxygen) -12.5% Lean Less than 0.4 V
      CAUTION:

      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 A017EWCE08 A017ES4E01 -
      2 A017EP5E03 A017ES4E01

      • Air fuel ratio sensor

      • Air fuel ratio sensor heater

      • Air fuel ratio sensor circuit
      3 A017EWCE08 A017EP5E03

      • Heated oxygen sensor

      • Heated oxygen sensor heater

      • Heated oxygen sensor circuit
      4 A017EP5E03 A017EP5E03

      • Fuel pressure

      • Gas leakage from exhaust system

        (Air fuel ratio extremely lean or rich)

      • Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.

      • To display the graph, enter the following menus on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / All Data / AFS Voltage B1S1 or AFS Voltage B2S1 and O2S B1S2 or O2S B2S2. Then press the graph button on the Data List view.

    Tip:

    • 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.

    • 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.

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PROCEDURE


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    CHECK 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 on (IG) and turn the tester on.

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

    4. Read the DTCs.

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

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


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    PERFORM ACTIVE TEST USING INTELLIGENT TESTER (AIR FUEL RATIO CONTROL)


    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 and ECT / 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 air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the tester.

      Tip:

      • 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 voltage
      Tester Display Injection Volumes Status Voltages
      AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio) +25% Rich Less than 3.1 V
      AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio) -12.5% Lean More than 3.4 V
      O2S B1S2 or O2S B2S2 (Heated oxygen) +25% Rich More than 0.55 V
      O2S B1S2 or O2S B2S2 (Heated oxygen) -12.5% Lean Less than 0.4 V
      Result
      Status AFS Voltage B1S1 or AFS Voltage B2S1 Status O2S B1S2 or O2S B2S2 Air Fuel Ratio Condition and Air Fuel Ratio and Heated Oxygen Sensor Conditions Misfires Suspected Trouble Areas Proceed to
      Lean/Rich Lean/Rich Normal -

      • Three-way catalyst converter

      • 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 lean actual air fuel ratio

      • Gas leakage from exhaust system

      		 D
      Rich Rich Actual air fuel ratio rich -

      • Extremely rich 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 more than 3.4 V, and the heated oxygen 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 heated oxygen sensor alternates correctly.


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    INSPECT FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leakage from the exhaust manifold sub-assembly and exhaust pipes.

      OK
      No gas leakage.

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    CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch on (IG) and turn the tester on.

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

    4. Read the DTCs.

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

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


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


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


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


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    INSPECT FOR EXHAUST GAS LEAK


    1. Inspect for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipes.

      OK
      No gas leaks.

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    INSPECT FOR EXHAUST GAS LEAK


    1. Inspect for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipes.

      OK
      No gas leaks.

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    GO TO DTC CHARTClick here

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    REPLACE AIR FUEL RATIO SENSORClick here

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    REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

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    REPLACE CENTER EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST)

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    REPLACE HEATED OXYGEN SENSORClick here

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    REPAIR OR REPLACE EXHAUST GAS LEAK POINT

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