SFI SYSTEM(w/ Canister Pump Module), Diagnostic DTC:P0420

DTC Code DTC Name
P0420 Catalyst System Efficiency Below Threshold (Bank 1)

MONITOR DESCRIPTION

The ECM uses air fuel ratio 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 (sensor 1), sends pre-catalyst information to the ECM. The second sensor, the air fuel ratio sensor (sensor 2), 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 output current of the air fuel ratio sensor (sensor 2) 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 30 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 air fuel ratio sensor (sensor 2) is long, the oxygen storage capacity is great. There is a direct correlation between the air fuel ratio sensor (sensor 2) 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 stored 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. Detection Item DTC Detection Condition Trouble Area MIL Memory
P0420 Catalyst System Efficiency Below Threshold (Bank 1) The oxygen storage capacity value is less than the standard value under active air fuel ratio control (1 trip detection logic).

  • Gas leak from exhaust system

  • Air fuel ratio sensor (sensor 1)

  • Air fuel ratio sensor (sensor 2)

  • Front exhaust pipe assembly (TWC: front catalyst)

  • Center exhaust pipe assembly (TWC: rear catalyst)

 Comes on DTC stored

CATALYST LOCATION

B008IM5C02
*1 Air Fuel Ratio Sensor (Sensor 1) *2 Air Fuel Ratio Sensor (Sensor 2)
*3 Exhaust Manifold *4

Front Exhaust Pipe Assembly

(TWC: Front Catalyst)
*5

Center Exhaust Pipe Assembly

(TWC: Rear Catalyst)

 - -

Note

Replacing the front exhaust pipe assembly (*4) and the center exhaust pipe assembly (*5) together when catalyst replacement is necessary. (Excluding air fuel ratio sensor (sensor 1) *1 and air fuel ratio sensor (sensor 2) *2).

MONITOR STRATEGY

Required Sensors/Components (Main)

Air fuel ratio sensor (sensor 1)

Air fuel ratio sensor (sensor 2)
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 73°C (163.4°F) or higher
Atmospheric pressure 76 kPa(abs) [570 mmHg(abs)] or higher
Idling Off
Engine speed Less than 4000 rpm
Air fuel ratio sensor status Activated
Fuel system status Closed loop
Engine load 10% or higher, and less than 80%
All of the following conditions are met -
Mass air flow rate 2.5 gm/sec or more, and less than 45 gm/sec.
Front catalyst temperature (estimated) 600°C (1112°F) or higher, and less than 840°C (1544°F)
Rear catalyst temperature (estimated) 400°C (752°F) or higher, and less than 800°C (1472°F)

Tech Tips

The estimated catalyst temperature can be read in the Data List using the GTS.

CONFIRMATION DRIVING PATTERN

Tech Tips


  • It is necessary for the response of the air fuel ratio sensor (sensor 2) to be normal in order to confirm DTC P042000. Therefore, perform the confirmation driving pattern for the air fuel ratio sensor (sensor 2) monitor before performing the confirmation driving pattern for the catalyst efficiency monitor.

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

B008H9VE03

  1. Connect the GTS to the DLC3.

  2. Turn the engine switch on (IG).

  3. Turn the GTS 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 GTS 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. With the shift lever in M, drive the vehicle at 60 km/h (37 mph), and then decelerate the vehicle by releasing the accelerator pedal for 5 seconds or more to perform the fuel-cut [C].

    CAUTION:

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

  10. Repeat step [C] 2 times or more in one driving cycle.

  11. Turn the engine switch off and wait for at least 30 seconds [D].

  12. Turn the engine switch on (IG) and turn the GTS on.

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

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

    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. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [G].

  16. 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.

  17. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

  18. Input the DTC: P0420.

  19. Check the DTC judgment result.

    GTS 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 is NORMAL, the system is normal.

    • If the judgment result is ABNORMAL, the system is malfunctioning.

    • If the judgment result is INCOMPLETE, perform the following procedure.

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

    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.

  21. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes [I].

  22. 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.

  23. Enter the following menus: Powertrain / Engine and ECT / Utility / All Readiness.

  24. Input the DTC: P0420.

  25. Check the DTC judgment result.

    GTS 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 is NORMAL, the system is normal.

    • If the judgment result is ABNORMAL, the system is malfunctioning.

CAUTION / NOTICE / HINT

Tech Tips


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

  • 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 GTS. 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)


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

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

    5. Read the DTCs.


      Powertrain > Engine and ECT > Trouble Codes
      Result
      Result Proceed to
      DTC P0420 is output A
      DTC P0420 and other DTCs are output B

      Tech Tips

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


    B

    GO TO DTC CHART Click here

    A

  2. PERFORM ACTIVE TEST USING GTS (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)


    1. Connect the GTS to the DLC3.

    2. Start the engine and warm it up.

    3. Turn the GTS on.

    4. Run the engine at an engine speed of 2500 rpm for approximately 90 seconds.

    5. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / AFS Current B1S1 and AFS Current B1S2.


      Powertrain > Engine and ECT > Active Test
      Active Test Display
      Control the Injection Volume for A/F Sensor
      Data List Display
      AFS Current B1S1
      AFS Current B1S2

    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 current outputs of the air fuel ratio sensor (sensor 1) and air fuel ratio sensor (sensor 2) (AFS Current B1S1 and AFS Current B1S2) displayed on the GTS.

      Tech Tips


      • Change the fuel injection volume within the range of -12.5% and +12.5%.

      • The air fuel ratio sensor (sensor 1) is displayed as AFS Current B1S1, and the air fuel ratio sensor (sensor 2) is displayed as AFS Current B1S2 on the GTS.

      • The air fuel ratio sensor (sensor 1) has an output delay of a few seconds and the air fuel ratio sensor (sensor 2) has a maximum output delay of approximately 20 seconds.

      • If the sensor output current does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

      Standard

      GTS Display

      (Sensor)

      		 Injection Volume Status Current

      AFS Current B1S1

      (Air fuel ratio (sensor 1))

      		 +12.5% Rich Below -0.075 mA
      -12.5% Lean More than 0.037 mA

      AFS Current B1S2

      (Air fuel ratio (sensor 2))

      		 +12.5% Rich Below -0.86 mA
      -12.5% Lean More than 0.33 mA
      Result
      Status of AFS Current B1S1 Status of AFS Current B1S2 Actual air fuel ratio, air fuel ratio sensor (sensor 1) and air fuel ratio sensor (sensor 2) condition 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 (sensor 1) malfunction

      • Air fuel ratio sensor (sensor 1)

      		 B
      Rich Lean/Rich Air fuel ratio sensor (sensor 1) malfunction

      • Air fuel ratio sensor (sensor 1)
      Lean/Rich Lean Air fuel ratio sensor (sensor 2) malfunction

      • Air fuel ratio sensor (sensor 2)

      • Gas leak from exhaust system

      		 C
      Lean/Rich Rich Air fuel ratio sensor (sensor 2) malfunction

      • Air fuel ratio sensor (sensor 2)

      • Gas leak from exhaust system
      Lean Lean Actual air fuel ratio lean

      • 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 the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor (sensor 1) output current (AFS Current B1S1) is consistently more than 0.037 mA, and the air fuel ratio sensor (sensor 2) output current (AFS Current B1S2) is consistently more than 0.33 mA.

      Rich: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor (sensor 1) output current (AFS Current B1S1) is consistently below -0.075 mA, and the air fuel ratio sensor (sensor 2) output current (AFS Current B1S2) is consistently below -0.86 mA.

      Lean/Rich: During the Control the Injection Volume for A/F Sensor Active Test, the output current of the air fuel ratio sensor (sensor 1) or air fuel ratio sensor (sensor 2) alternate correctly.


    B

    REPLACE AIR FUEL RATIO SENSOR (SENSOR 1) 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.
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

    OK

  4. REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST) AND CENTER EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST)

    Note

    Replace the front exhaust pipe assembly (TWC: Front catalyst) and the center 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. Replace the front exhaust pipe assembly (TWC: Front catalyst).

      Click here

    2. Replace the center exhaust pipe assembly (TWC: Rear catalyst).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    END

  5. 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

      Result
      Proceed to
      NEXT

    NEXT

  6. CLEAR DTC


    1. Connect the GTS to the DLC3.

    2. Turn the engine switch on (IG).

    3. Turn the GTS on.

    4. Clear the DTCs.


      Powertrain > Engine and ECT > Trouble Codes

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

      Result
      Proceed to
      NEXT

    NEXT

  7. CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)


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

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


      Powertrain > Engine and ECT > Trouble Codes

    3. Read the DTCs.

      Result
      Result Proceed to
      DTC P0420 is output A

      DTC is not output

      (Pending DTC is not output)

      		 B

    B

    END

    A

  8. REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST) AND CENTER EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST)

    Note

    Replace the front exhaust pipe assembly (TWC: Front catalyst) and the center 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. Replace the front exhaust pipe assembly (TWC: Front catalyst).

      Click here

    2. Replace the center exhaust pipe assembly (TWC: Rear catalyst).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    END

  9. REPLACE AIR FUEL RATIO SENSOR (SENSOR 1)


    1. Replace the air fuel ratio sensor (sensor 1).

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the air fuel ratio sensor (sensor 1).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 7 Click here

  10. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 5 Click here

    OK

  11. REPLACE AIR FUEL RATIO SENSOR (SENSOR 2)


    1. Replace the air fuel ratio sensor (sensor 2).

      Click here

      Tech Tips

      Perform "Inspection After Repair" after replacing the air fuel ratio sensor (sensor 2).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 7 Click here

  12. CHECK FOR EXHAUST GAS LEAK


    1. Check the exhaust gas leaks.

      OK
      No gas leaks.
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 5 Click here

    OK

  13. 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 Procedure.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 7 Click here