SFI SYSTEM, Diagnostic DTC:P0420, P0430

DTC Code DTC Name
P0420 Catalyst System Efficiency Below Threshold (Bank 1)
P0430 Catalyst System Efficiency Below Threshold (Bank 2)

DESCRIPTION

The ECM uses the sensors mounted in front of and behind the three-way catalytic converter 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, rather than the conventional detecting method, which uses the locus ratio.

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 a rich-lean cycle of the heated oxygen sensor is long, the oxygen storage capacity becomes greater. There is a direct correlation between the oxygen storage capacities of the heated oxygen sensor and 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, it illuminates the MIL and sets a DTC.

DTC No. DTC Detection Condition Trouble Area
P0420 Oxygen storage capacity value smaller than standard value under active air fuel ratio control (2 trip detection logic)

  • Gas leakage from exhaust system

  • Air fuel ratio sensor (bank 1 sensor 1)

  • Heated oxygen sensor (bank 1 sensor 2)

  • Exhaust manifold (three-way catalytic converter)
P0430 Oxygen storage capacity value smaller than standard value under active air fuel ratio control (2 trip detection logic)

  • Gas leakage from exhaust system

  • Air fuel ratio sensor (bank 2 sensor 1)

  • Heated oxygen sensor (bank 2 sensor 2)

  • Exhaust manifold (three-way catalytic converter)

CONDITIONING FOR SENSOR TESTING

Tech Tips

Perform the operation with the engine speeds and durations described below prior to checking the waveforms of the air fuel ratio and heated oxygen sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.

A017DJKE28

  1. Connect the intelligent tester to the DLC3 (Procedure "A").

  2. Start the engine and warm it up with all the accessories switched off, until the engine coolant temperature stabilizes (Procedure "B").

  3. Run the engine at an engine speed of between 2500 rpm and 3000 rpm for at least 3 minutes (Procedure "C").

  4. While running the engine at 3000 rpm for 2 seconds and at 2000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the tester (Procedure "D").

    Tech Tips


    • If either of the voltage outputs of the air fuel ratio or heated oxygen sensor does not fluctuate, or either of the sensors makes a noise, 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 following Control the Injection Volume for A/F Sensor using the intelligent tester.

    • 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).

A017E8UE10

  1. AIR FUEL RATIO CONTROL

    Tech Tips

    Intelligent tester only:

    Malfunctioning areas can be identified by performing the Control the Injection Volume for air fuel ratio sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the air fuel ratio sensor, heated oxygen sensor and other potential trouble areas are malfunctioning.

    The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using an intelligent tester.


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and turn the tester on.

    3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

    4. On the tester, select the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

    5. Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

    6. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.

      Tech Tips


      • The Control the Injection Volume for air fuel ratio sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.

      • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

      CAUTION:

      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.

      Case

      Air Fuel Ratio Sensor (Sensor 1)

      Output Voltage

      Heated Oxygen Sensor (Sensor 2)

      Output Voltage

      		 Main Suspected Trouble Area
      1 A017EWCE01 A017EFTE02 -
      2 A017EP5E01 A017EFTE02

      • Air fuel ratio sensor

      • Air fuel ratio sensor heater

      • Air fuel ratio sensor circuit
      3 A017EWCE01 A017EP5E01

      • Heated oxygen sensor

      • Heated oxygen sensor heater

      • Heated oxygen sensor circuit
      4 A017EP5E01 A017EP5E01

      • Fuel pressure

      • Gas leakage from exhaust system

        (Air fuel ratio extremely lean or rich)

INSPECTION PROCEDURE

Tech Tips

Read freeze frame data using the intelligent tester. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.

PROCEDURE


  1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 AND/OR P0430)


    1. Connect the intelligent tester to the DLC3.

    2. Turn the ignition switch on (IG) and turn the tester on.

    3. Select the following menu items: Powertrain / Engine and ECT / DTC.

    4. Read the DTCs.

      Result
      Display (DTC Output) Proceed to
      P0420 and/or P0430 A
      P0420 and/or P0430 and other DTCs B

      Tech Tips

      If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.


    B

    GO TO DTC CHART Click here

    A

  2. PERFORM ACTIVE TEST USING INTELLIGENT TESTER (AIR FUEL RATIO CONTROL)


    1. Connect the intelligent tester to the DLC3.

    2. Start the engine and turn the tester on.

    3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

    4. Select the following menu items on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

    5. Perform the Control the Injection Volume for A/F Sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).

    6. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS B1S1 and O2S B1S2 or AFS B2S1 and O2S B2S2) displayed on the tester.

      Tech Tips


      • The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.

      • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

      Standard voltage
      Tester Display (Sensor) Injection Volume Status Voltage
      AFS B1S1 or AFS B2S1 (Air fuel ratio) +25% Rich Less than 3.0
      AFS B1S1 or AFS B2S1 (Air fuel ratio) -12.5% Lean More than 3.35
      O2S B1S2 or O2S B2S2 (Heated oxygen) +25% Rich More than 0.55
      O2S B1S2 or O2S B2S2 (Heated oxygen) -12.5% Lean Less than 0.4
      Result
      Status AFS B1S1 or AFS B2S1 Status O2S B1S2 or O2S B2S2 Air Fuel Ratio Condition and Air Fuel Ratio and Heated Oxygen Sensor Condition Misfire Suspected Trouble Area Proceed to
      Lean/Rich Lean/Rich Normal -

      • Three-way catalytic converter

      • Gas leakage 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 B
      Lean/Rich Lean Heated oxygen sensor malfunction -

      • Heated oxygen sensor

      • Gas leakage from exhaust system

      		 C
      Lean/Rich Rich Heated oxygen sensor malfunction -

      • Heated oxygen sensor

      • Gas leakage from exhaust system

      		 C
      Lean Lean Actual air fuel ratio lean May occur

      • Extremely rich or lean actual air fuel ratio

      • Gas leakage from exhaust system

      		 A
      Rich Rich Actual air fuel ratio rich -

      • Extremely rich or lean actual air fuel ratio

      • Gas leakage from exhaust system

      		 A

      Lean: During Control the Injection Volume for A/F Sensor, the air fuel ratio sensor output voltage (AFS) is consistently more than 3.35 V, and the heated oxygen sensor output voltage (O2S) is consistently less than 0.4 V.

      Rich: During Control the Injection Volume for A/F Sensor, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.

      Lean/Rich: During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the HO2 sensor alternates correctly.


    B

    REPLACE AIR FUEL RATIO SENSOR Click here

    C

    CHECK FOR EXHAUST GAS LEAKS Click here

    A

  3. CHECK FOR EXHAUST GAS LEAKS


    1. Check for exhaust gas leakage.

      OK
      No gas leakage

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

    OK

    REPLACE THREE-WAY CATALYTIC CONVERTER (EXHAUST MANIFOLD LH OR RH)

  4. CHECK FOR EXHAUST GAS LEAKS


    1. Check for exhaust gas leakage.

      OK
      No gas leakage

    NG

    REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT

    OK

    CHECK AND REPLACE HEATED OXYGEN SENSOR