SFI SYSTEM(w/o EGR 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 15 to 20 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)

Comes on

DTC stored

CATALYST LOCATION

A378114C01

*1

Exhaust Manifold Converter Sub-assembly

TWC: Front Catalyst

*2

Air Fuel Ratio Sensor (Sensor 1)

*3

Front Exhaust Pipe Assembly

TWC: Rear Catalyst

*4

Heated Oxygen Sensor (Sensor 2)

*5

Center Exhaust Pipe Assembly

*6

Tail Exhaust Pipe Assembly
Note:

If DTC P0420 is output, replace the exhaust manifold converter sub-assembly (*1) and the front exhaust pipe assembly (*3) together when catalyst replacement is necessary (Excluding air fuel ratio sensor*2 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

1, 2 and 3

1. Mass air flow

2.5 gm/sec or more, and less than 50 gm/sec

2. Front catalyst temperature (estimated)

530°C (986°F) or higher, and less than 770°C (1418°F)

3. Rear catalyst temperature (estimated)

400°C (752°F) or higher, and less than 700°C (1292°F)
Tip:

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

CONFIRMATION DRIVING PATTERN

Tip:

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

A283969E56

  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.

    Tip:

    • 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.

    Tip:

    • 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.

    Tip:

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

    • If a pending DTC is not output, perform the following procedure.

  17. With the engine running, 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.

    Tip:

    • 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.

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

  19. 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.

CONDITIONING FOR SENSOR TESTING

Tip:

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.

A270243E06

  • (a) Connect the GTS to the DLC3.

  • (b) Turn the power switch on (IG) and turn the GTS on [A].

  • (c) Put the engine in inspection mode (maintenance mode).

    Click here

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

  • (e) Run the engine at an engine speed of 2500 rpm for at least 3 minutes [C].

    Tip:

    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, perform step [C] after charging control has completed.

  • (f) While running the engine at 2500 rpm and 1500 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the GTS [D].

Tip:

  • If the voltage output of either the air fuel ratio or heated oxygen sensor does not fluctuate, or there is a 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 for A/F Sensor Active Test using the GTS.

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

A199479E21

CAUTION / NOTICE / HINT

Tip:

  • 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
      Tip:

      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 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 / Ptrl AF Control / 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 12.5% or -12.5% 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.

      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 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 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

      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

      D

      Rich

      Rich

      Actual air fuel ratio rich

      -

      • Extremely rich actual air fuel ratio

      • Gas leak from exhaust system

      Lean: During Control the Injection Volume for A/F Sensor Active Test, 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 for A/F Sensor Active Test, AFS Voltage B1S1 is consistently below 3.1 V, and O2S B1S2 is consistently higher than 0.55 V.

      Lean/Rich: During Control the Injection Volume for A/F Sensor Active Test, the output voltage of the air fuel ratio sensor and heated oxygen sensor alternate correctly.

    B

    REPLACE AIR FUEL RATIO SENSORClick here

    C

    CHECK FOR EXHAUST GAS LEAKClick here

    D

    CHECK FOR EXHAUST GAS LEAKClick here

    A

  3. CHECK FOR EXHAUST GAS LEAK

    1. Check for exhaust gas leaks.

      OK

      No gas leaks.

    Result

    Proceed to

    OK

    NG
    OK

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

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINTClick here

  4. REPLACE AIR FUEL RATIO SENSOR

    1. Replace the air fuel ratio sensor.

      Click here

      Tip:

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

      Click here

    Result

    Proceed to

    NEXT
    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIREDClick here

  5. 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 POINTClick here

    OK

  6. REPLACE HEATED OXYGEN SENSOR

    1. Replace the heated oxygen sensor.

      Click here

      Tip:

      Perform "Inspection After Repair" after replacing the heated oxygen sensor.

      Click here

    Result

    Proceed to

    NEXT
    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIREDClick here

  7. 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 POINTClick here

    OK

  8. 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 or P0172 Inspection Procedure.

      Click here

    Result

    Proceed to

    NEXT
    NEXT

    CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIREDClick here

  9. REPAIR OR REPLACE EXHAUST GAS LEAK POINT

    1. Repair or replace exhaust gas leak point.

      Tip:

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

      Click here

    Result

    Proceed to

    NEXT
    NEXT

  10. CONFIRM WHETHER MALFUNCTION HAS BEEN SUCCESSFULLY REPAIRED

    1. Connect the GTS to the DLC3.

    2. Turn the power switch on (IG).

    3. Turn the GTS on.

    4. Clear the DTCs.

      Click here

      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 pending DTCs.

      Powertrain > Engine and ECT > Trouble Codes

      Result

      Result

      Proceed to

      DTC P0420 is output

      A

      DTCs are not output

      B
    B

    END

    A

  11. 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.

    Tip:

    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