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 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. DTC Detection Condition Trouble Area
P0420 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

CATALYST LOCATION

A01HULXE01
Text in Illustration
*1 Air Fuel Ratio Sensor (Sensor 1) *2 Heated Oxygen Sensor (Sensor 2)
*3 TWC: Front Catalyst *4 TWC: Rear Catalyst
*5 Center Exhaust Pipe Assembly *6 Tail Exhaust Pipe Assembly
*7 Exhaust Manifold Converter Sub-assembly *8 Front Exhaust Pipe Assembly

Note

Replace the exhaust manifold converter sub-assembly (*7) and the front exhaust pipe assembly (*8) together when catalyst replacement is necessary. (Excluding air fuel ratio sensor *1 and heated oxygen sensor *2)

MONITOR STRATEGY

Related DTCs P0420: Catalyst deterioration
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
Duration Approximately 30 seconds
MIL Operation 2 driving cycles
Sequence of Operation None

TYPICAL ENABLING CONDITIONS

Monitor runs whenever the following DTCs are not stored

P0010 (VVT oil control valve)

P0011 (VVT system - advance)

P0012 (VVT system - retard)

P0016 (VVT system - misalignment)

P0031, P0032, P101D (Air fuel ratio sensor heater)

P0037, P0038, P102D (Heated oxygen sensor heater)

P0102, P0103 (Mass air flow meter)

P0107, P0108 (Manifold absolute pressure)

P0115, P0117, P0118 (Engine coolant temperature sensor)

P0120, P0121, P0122, P0123, P0220, P0222, P0223, P2135 (Throttle position sensor)

P0125 (Insufficient coolant temperature for closed loop fuel control)

P0136, P0137, P0138, P0139, P0607 (Heated oxygen sensor)

P014C, P014D, P015A, P015B, P2195, P2196, P2237, P2238, P2239, P2252, P2253 (Air fuel ratio sensor)

P0171, P0172 (Fuel system)

P0301, P0302, P0303, P0304 (Misfire)

P0335 (Crankshaft position sensor)

P0340, P0342, P0343 (Camshaft position sensor)

P0351, P0352, P0353, P0354 (Igniter)

P0401 (EGR system (closed))

P219A (Air fuel ratio imbalance)
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 50 gm/sec
Front catalyst temperature (estimated) 530°C (986°F) or higher, and less than 770°C (1418°F)
Rear catalyst temperature (estimated) 420°C (788°F) or higher, and less than 700°C (1418°F)

TYPICAL MALFUNCTION THRESHOLDS

Oxygen Storage Capacity (OSC) of Three-Way Catalytic Converter (TWC) Less than 0.2 g

MONITOR RESULT

Refer to detailed information in Checking Monitor Status Click here.

P0420: Catalyst Efficiency / O2 STORAGE B1
Monitor ID Test ID Scaling Unit Description
$21 $A9 Multiply by 0.0003 No dimension Oxygen storage capacity of catalyst bank 1

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.

A01HVTCE38

  1. Connect the Techstream to the DLC3.

  2. Turn the power switch on (IG)

  3. Turn the Techstream 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 Techstream on.

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

  8. Check that Catalyst Efficiency / Current is Incomplete.

  9. Put the engine in inspection mode (maintenance mode) Click here.

  10. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher with the shift lever in P [A].

    Tech Tips

    In order to keep the idling stable, turn off the A/C and all other electric loads and do not perform any shift operations.

  11. 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.

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

  13. Turn the power switch on (IG) and turn the Techstream on.

  14. Put the engine in inspection mode (maintenance mode) Click here.

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

  16. 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.

    • The monitor item change to Complete as the Catalyst Efficiency monitor operates.

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

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

    Tech Tips

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

  19. Drive the vehicle at approximately 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.

    • The monitor item will change to Complete as the Catalyst Efficiency monitor operates.

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

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

    Tech Tips

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

  22. If no pending DTC is output, perform a universal trip and check for permanent DTCs Click here.

    Tech Tips


    • If a permanent DTC is output, the system is malfunctioning.

    • If no permanent DTC is output, the system is normal.

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.

A01HTVDE56

Tech Tips


  • If either of the voltage outputs of the air fuel ratio or heated oxygen sensor does not fluctuate, or there is noise in the waveform of either sensor, 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 Control the Injection Volume Active Test using the Techstream.

  • 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).

A01HW03E09

INSPECTION PROCEDURE

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 Techstream. 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 Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the Techstream on.

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

    5. Read the DTCs.

      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 TECHSTREAM (CONTROL THE INJECTION VOLUME)


    1. Connect the Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the Techstream on.

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

    5. Start the engine and warm it up.

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

      Tech Tips

      During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.

    7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / GAS AF Control / AFS Voltage B1S1 and 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 Techstream.

      Tech Tips


      • Change the fuel injection volume within the range of - 12% to 12%. The injection volume can be changed in fine gradations.

      • 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

      Techstream Display

      (Sensor)

      		 Injection Volume Status Voltage

      AFS Voltage B1S1

      (Air fuel ratio)

      		 12% Rich Below 3.1 V
      -12% Lean Higher than 3.4 V

      O2S B1S2

      (Heated oxygen)

      		 12% Rich Higher than 0.55 V
      -12% Lean Below 0.4 V
      Result

      Status

      AFS Voltage B1S1

      Status

      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: During Control the Injection Volume, 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: During Control the Injection Volume, the AFS Voltage B1S1 is consistently below 3.1 V, and the O2S B1S2 is consistently higher than 0.55 V.

      • Lean/Rich: During Control the Injection Volume of the Active Test, the output voltage of the air fuel ratio sensor and 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.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

    OK

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


    1. Connect the Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the Techstream on.

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

    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 / Primary / Throttle Idle Position and MAP.

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

      Tech Tips


      • 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 30 steps or more during the Active Test.

      OK
      MAP and idling condition 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 30 Steps

      Idling condition

      (Throttle Idle Position: ON)

      		 Steady idling Idling changes from steady to rough idling or engine stalls

      MAP

      (Data List)

      MAP value is 20 to 40 kPa(abs) [150 to 300 mmHg(abs)]

      (EGR valve is fully closed)

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

      Tech Tips

      During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in the EGR valve.

      Result
      Result Proceed to
      NG A
      OK B

    B

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

    A

  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.


    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

    Replace 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 the 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.


    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.


    NEXT

    CHECK WHETHER DTC OUTPUT RECURS (DTC P0420) Click here

  8. CHECK FOR EXHAUST GAS LEAK


    1. Check for exhaust gas leaks.

      OK
      No gas leaks.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

    OK

  9. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor Click here.


    NEXT

    CHECK WHETHER DTC OUTPUT RECURS (DTC P0420) Click here

  10. CHECK FOR EXHAUST GAS LEAK


    1. Check the exhaust gas leaks.

      OK
      No gas leaks.

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

    OK

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


    1. Connect the Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the Techstream on.

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

    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 / Primary / Throttle Idle Position and MAP.

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

      Tech Tips


      • 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 30 steps or more during the Active Test.

      OK
      MAP and idling condition 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 30 Steps

      Idling condition

      (Throttle Idle Position: ON)

      		 Steady idling Idling changes from steady to rough idling or engine stalls

      MAP

      (Data List)

      MAP value is 20 to 40 kPa(abs) [150 to 300 mmHg(abs)]

      (EGR valve is fully closed)

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

      Tech Tips

      During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in the EGR valve.

      Result
      Result Proceed to
      NG A
      OK B

    B

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

    A

  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.


    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.


    NEXT

    CHECK WHETHER DTC OUTPUT RECURS (DTC P0420) Click here

  14. 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.


    NEXT

  15. CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)


    1. Connect the Techstream to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the Techstream on.

    4. Clear the DTCs Click here.

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

    6. Turn the power switch on (IG).

    7. Turn the Techstream on.

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

    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.

      Result
      Result Proceed to
      DTC P0420 is output A

      DTC is 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

    Replace 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 the 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.


    NEXT

    END