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 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 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)

  • Heated oxygen sensor (sensor 2)

  • Exhaust manifold converter sub-assembly (TWC: Front catalyst) and front No. 2 exhaust pipe sub-assembly (TWC: Rear catalyst)

 Comes on DTC stored

CATALYST LOCATION

A01QOJOC01
*1 Air Fuel Ratio Sensor (Sensor 1) *2 Heated Oxygen Sensor (Sensor 2)
*3

Exhaust Manifold Converter Sub-assembly

(TWC: Front Catalyst)

 *4

Front No. 2 Exhaust Pipe Sub-assembly

(TWC: Rear Catalyst)
*5 Center Exhaust Pipe Assembly *6 Tail Exhaust Pipe Assembly
*7 Front Exhaust Pipe Sub-assembly - -

Note

Replace the exhaust manifold converter sub-assembly (*3) and the front No. 2 exhaust pipe sub-assembly (*4) together when catalyst replacement is necessary. (Excluding air fuel ratio sensor *1 and heated oxygen sensor *2)

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

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 90%
Shift position 3rd or higher
All of the following conditions are met -
Mass air flow rate 1.5 gm/sec or more, and less than 75 gm/sec.
Front catalyst temperature (estimated) 540°C (1004°F) or higher, and less than 880°C (1616°F)
Rear catalyst temperature (estimated) 380°C (716°F) or higher, and less than 770°C (1418°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 that the response of the heated oxygen sensor is normal in order to confirm DTC P0420. Therefore, perform the driving pattern for the heated oxygen sensor monitor before performing the drive 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.

A01QQW5E01

  1. Connect the GTS to the DLC3.

  2. Turn the ignition switch to ON.

  3. Turn the GTS on.

  4. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure).

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

  6. Turn the ignition switch to ON and turn the GTS on.

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

  8. Check that Catalyst Efficiency / Current is Incomplete.

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

  10. 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.

  11. With the shift lever in S, 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.

  12. Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor / O2 Sensor / RL F/C B1S2 [D].

  13. Check the Test Value for RL F/C B1S2.


    • If Test Value displays a value larger than 0, perform the following procedure, as the O2 sensor monitor is finished.

    • If Test Value displays 0, perform step [C] until it displays a value larger than 0, as the O2 sensor monitor is not finished.

  14. Turn the ignition switch off and wait for at least 30 seconds [F].

  15. Turn the ignition switch to ON and turn the GTS on.

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

  17. Drive the vehicle at approximately 60 km/h (37 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.

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

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

  19. Check if any DTCs are stored.

    Tech Tips

    If the monitor item does not change to Complete, and no DTCs are stored, 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 [J].

    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 [K].

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

  22. Check if any DTCs are stored.

    Tech Tips

    If the monitor item does not change to Complete, and no DTCs are stored, drive the vehicle again under an increased load.

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.

A01QOINE04

Tech Tips


  • 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 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).

A01QPZPE09

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 ignition switch to ON.

    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 / GAS 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

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

      Tech Tips


      • Change the fuel injection volume within the range of -12.5% and +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 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 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.
      Result
      Proceed to
      OK
      NG

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAK POINT Click here

    OK

  4. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY (TWC: FRONT CATALYST) AND FRONT NO. 2 EXHAUST PIPE SUB-ASSEMBLY (TWC: REAR CATALYST)

    Note

    Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst) and the front No. 2 exhaust pipe sub-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 No. 2 exhaust pipe sub-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. CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)


    1. Connect the GTS to the DLC3.

    2. Turn the ignition switch to ON.

    3. Turn the GTS on.

    4. Clear the DTCs.

      Click here


      Powertrain > Engine and ECT > Clear DTCs

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

    6. Turn the ignition switch to ON.

    7. Turn the GTS on.

    8. Start the engine.

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

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

    11. Read the DTCs.


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

      DTC is not output

      (No pending DTCs output)

      		 B

    B

    END

    A

  7. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY (TWC: FRONT CATALYST) AND FRONT NO. 2 EXHAUST PIPE SUB-ASSEMBLY (TWC: REAR CATALYST)

    Note

    Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst) and the front No. 2 exhaust pipe sub-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 No. 2 exhaust pipe sub-assembly (TWC: Rear catalyst).

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    END

  8. 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 6 Click here

  9. 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

  10. REPLACE HEATED OXYGEN SENSOR


    1. Replace the heated oxygen sensor.

      Click here

      Tech Tips

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

      Click here

      Result
      Proceed to
      NEXT

    NEXT

    GO TO STEP 6 Click here

  11. 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

  12. 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 6 Click here