SFI SYSTEM, Diagnostic DTC:P0420

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

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 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 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 will illuminate the MIL and store a 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 (2 trip detection logic).

  • Gas leak from exhaust system

  • Air fuel ratio sensor (sensor 1)

  • Heated oxygen sensor (sensor 2)

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

  • EGR valve assembly

 Comes on DTC stored

CATALYST LOCATION

B008GCFC02
*1 Exhaust Manifold Converter Sub-assembly (TWC: Front Catalyst) *2 Front Exhaust Pipe Assembly (TWC: Rear Catalyst)
*3 Air Fuel Ratio Sensor (Sensor 1) *4 Heated Oxygen Sensor (Sensor 2)
*5 Tail Exhaust Pipe Assembly *6 Tail Exhaust Pipe LH

Note

Replace the exhaust manifold converter sub-assembly (*1) and the front exhaust pipe assembly (*2) together when catalyst replacement is necessary. (Excluding air fuel ratio sensor (*3) 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

Auxiliary 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 4000 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 -
Mass air flow rate 2.5 gm/sec or more, and less than 45 gm/sec
Front catalyst temperature (estimated) 500°C (932°F) or higher, and less than 770°C (1418°F)
Rear catalyst temperature (estimated) 400°C (752°F) or higher, and less than 700°C (1292°F)

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.

B008GI0E40

  1. Connect the GTS to the DLC3.

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

  6. Turn the power switch on (IG) and turn the GTS on.

  7. Put the engine in inspection mode (maintenance mode).

    Click here

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

  9. With the engine running, drive the vehicle at approximately 75 km/h (47 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.

    • If the engine stops, further depress the accelerator pedal to restart the engine.

  10. Turn the power switch off and wait for at least 30 seconds [C].

  11. Turn the power switch on (IG) and turn the GTS on.

  12. Put the engine in inspection mode (maintenance mode).

    Click here

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

  14. With the engine running, drive the vehicle at approximately 75 km/h (47 mph) for 10 minutes or more [E].

    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.

    • If the engine stops, further depress the accelerator pedal to restart the engine.

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

  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 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 and no pending DTC is output, perform the following procedure.

  20. With the engine running, drive the vehicle at 100 km/h (62 mph) for 10 minutes or more [G].

    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.

    • If the engine stops, further depress the accelerator pedal to restart the engine.

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

  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 shows NORMAL, the system is normal.

    • If the judgment result shows ABNORMAL, the system has a malfunction.

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.

B008GFZE03

B008GGCE09

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 inspection 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 power 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. Turn the power switch on (IG).

    3. Turn the GTS on.

    4. Put the engine in inspection mode (maintenance mode).

      Click here


      Powertrain > Hybrid Control > Utility
      Tester Display
      Inspection Mode

    5. Start the engine and warm it up.

    6. Idle the engine for 5 minutes or more with the shift lever in P.

    7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / AFS Voltage B1S1 and O2S B1S2.


      Powertrain > Engine and ECT > Active Test
      Active Test Display
      Control the Injection Volume for A/F Sensor
      Data List Display
      AFS Voltage B1S1
      O2S B1S2

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

    9. Monitor the voltage outputs of the air fuel ratio sensor and heated oxygen sensor (AFS Voltage B1S1 and O2S B1S2) displayed on the GTS.

      Tech Tips


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

      • 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

      GTS Display

      (Sensor)

      		 Injection Volume Status Voltage

      AFS Voltage B1S1

      (Air fuel ratio)

      		 12.5% Rich Below 3.1 V
      -12.5% Lean Higher than 3.4 V

      O2S B1S2

      (Heated oxygen)

      		 12.5% Rich Higher than 0.55 V
      -12.5% Lean Below 0.4 V
      Result
      Status of AFS Voltage B1S1 Status of O2S B1S2 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

      • EGR valve assembly

      		 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 lean actual air fuel ratio

      • Gas leak from exhaust system

      • EGR valve assembly

      		 D
      Rich Rich Actual air fuel ratio rich -

      • Extremely rich actual air fuel ratio

      • Gas leak from exhaust system

      • EGR valve assembly

      • Lean: While performing Control the Injection Volume for A/F Sensor, the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.

      • Rich: While performing Control the Injection Volume for A/F Sensor, AFS Voltage B1S1 is consistently below 3.1 V, and the O2S B1S2 is consistently higher than 0.55 V.

      • Lean/Rich: While performing Control the Injection Volume for A/F Sensor, the output voltages of the air fuel ratio sensor or the 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.
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 14 Click here

    OK

  4. PERFORM ACTIVE TEST USING GTS (CONTROL THE EGR STEP POSITION)


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

    4. Put the engine in inspection mode (maintenance mode).

      Click here


      Powertrain > Hybrid Control > Utility
      Tester Display
      Inspection Mode

    5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

      Tech Tips

      The A/C switch and all accessory switches should be off.

    6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position / Data List / MAP and Throttle Idle Position.


      Powertrain > Engine and ECT > Active Test
      Active Test Display
      Control the EGR Step Position
      Data List Display
      MAP
      Throttle Idle Position

    7. Confirm that the Throttle Idle Position is ON and check the MAP values in the Data List while performing the Active Test.

      Note


      • Do not leave the EGR valve open for 10 seconds or more during the Active Test.

      • Be sure to return the EGR valve to step 0 when the Active Test is completed.

      • Do not open the EGR valve 26 steps or more during the Active Test.

      OK
      MAP change in response to EGR step position when Throttle Idle Position is ON in Data List.
      Standard
      - EGR Step Position (Active Test)
      0 Steps 0 to 26 Steps

      MAP

      (Data List)

      		 (EGR valve is fully closed) MAP value is at least +10 kPa (75 mmHg) higher than when EGR valve is fully closed

      Tech Tips


      • While performing the Active Test, if the increase in the value of MAP is small, the EGR valve assembly may be a malfunctioning.

      • Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of MAP may occur while performing the Active Test. However, the amount that the value of MAP increases will be smaller than normal.

      Result
      Proceed to
      OK
      NG

    OK

    GO TO STEP 6 Click here

    NG

  5. INSPECT EGR VALVE ASSEMBLY


    1. Remove the EGR valve assembly.

      Click here

    2. Check if the EGR valve is stuck open.

      OK
      EGR valve is tightly closed.

      Tech Tips

      Perform "Inspection After Repair" after replacing the EGR valve assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE EGR VALVE ASSEMBLY Click here

    OK

  6. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY (TWC: FRONT CATALYST) AND FRONT EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST)

    Note

    When replacing the exhaust manifold converter sub-assembly (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 Catalyst Location.


    1. Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst).

      Click here

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

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    END

  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

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 15 Click here

  8. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.
      Result
      Proceed to
      OK
      NG

    NG

    GO TO STEP 14 Click here

    OK

  9. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 15 Click here

  10. 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

  11. PERFORM ACTIVE TEST USING GTS (CONTROL THE EGR STEP POSITION)


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

    4. Put the engine in inspection mode (maintenance mode).

      Click here


      Powertrain > Hybrid Control > Utility
      Tester Display
      Inspection Mode

    5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

      Tech Tips

      The A/C switch and all accessory switches should be off.

    6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position / Data List / MAP and Throttle Idle Position.


      Powertrain > Engine and ECT > Active Test
      Active Test Display
      Control the EGR Step Position
      Data List Display
      MAP
      Throttle Idle Position

    7. Confirm that the Throttle Idle Position is ON and check the MAP values in the Data List while performing the Active Test.

      Note


      • Do not leave the EGR valve open for 10 seconds or more during the Active Test.

      • Be sure to return the EGR valve to step 0 when the Active Test is completed.

      • Do not open the EGR valve 26 steps or more during the Active Test.

      OK
      MAP change in response to EGR step position when Throttle Idle Position is ON in Data List.
      Standard
      - EGR Step Position (Active Test)
      0 Steps 0 to 26 Steps

      MAP

      (Data List)

      		 (EGR valve is fully closed) MAP value is at least +10 kPa (75 mmHg) higher than when EGR valve is fully closed

      Tech Tips


      • While performing the Active Test, if the increase in the value of MAP is small, the EGR valve assembly may be malfunctioning.

      • Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of MAP may occur while performing the Active Test. However, the amount that the value of MAP increases will be smaller than normal.

      Result
      Proceed to
      OK
      NG

    OK

    GO TO STEP 13 Click here

    NG

  12. INSPECT EGR VALVE ASSEMBLY


    1. Remove the EGR valve assembly.

      Click here

    2. Check if the EGR valve is stuck open.

      OK
      EGR valve is tightly closed.

      Tech Tips

      Perform "Inspection After Repair" after replacing the EGR valve assembly.

      Click here

      Result
      Proceed to
      OK
      NG

    NG

    REPLACE EGR VALVE ASSEMBLY 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 Inspection Procedure.

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 15 Click here

  14. REPAIR OR REPLACE EXHAUST GAS LEAK POINT


    1. Repair or replace the exhaust gas leak point.

      Tech Tips

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

      Click here

      Result
      Proceed to
      NEXT

    NEXT

  15. CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)


    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

    4. Clear the DTCs.


      Powertrain > Engine and ECT > Clear DTCs

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

    6. Turn the power switch on (IG).

    7. Turn the GTS on.

    8. Put the engine in inspection mode (maintenance mode).

      Click here


      Powertrain > Hybrid Control > Utility
      Tester Display
      Inspection Mode

    9. Start the engine.

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

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

    12. Read the DTCs.


      Powertrain > Engine and ECT > Trouble Codes
      Result
      Result Proceed to
      DTC P0420 is output A

      DTCs are not output

      (No pending DTCs output)

      		 B

    B

    END

    A

  16. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY (TWC: FRONT CATALYST) AND FRONT EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST)

    Note

    When replacing the exhaust manifold converter sub-assembly (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 Catalyst Location.


    1. Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst).

      Click here

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

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    END