DTC    P0420    Catalyst System Efficiency Below Threshold (Bank 1)

DTC    P0430    Catalyst System Efficiency Below Threshold (Bank 2)

for Preparation Click here


DESCRIPTION

The ECM uses the sensors mounted in front of and behind the Three-Way Catalytic Converter (TWC) to monitor its efficiency.
The first sensor, the Air-Fuel Ratio (A/F) sensor, sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor, sends post-catalyst information to the ECM.
In order to detect any deterioration in the TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the HO2 sensor while performing active air- fuel ratio control, rather than the conventional detecting method, which uses the locus ratio.
The OSC value is an indication of the oxygen storage capacity of the TWC. 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 level. If a rich-lean cycle of the HO2 sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the HO2 sensor and the TWC.
The ECM uses the OSC value to determine the state of the TWC. If any deterioration has occurred, it illuminates the MIL and sets a DTC.

DTC No.
DTC Detection Condition
Trouble Area
P0420
OSC value is smaller than standard value under active air-fuel ratio control (2 trip detection logic)
  1. Gas leakage from exhaust system
  2. A/F sensor (bank 1 sensor 1)
  3. HO2 sensor (bank 1 sensor 2)
  4. Exhaust manifold (TWC)
P0430
OSC value is smaller than standard value under active air-fuel ratio control (2 trip detection logic)
  1. Gas leakage from exhaust system
  2. A/F sensor (bank 2 sensor 1)
  3. HO2 sensor (bank 2 sensor 2)
  4. Exhaust manifold (TWC)

HINT:
  1. Bank 1 refers to the bank that includes cylinder No. 1.
  2. Bank 2 refers to the bank that does not include cylinder No. 1.
  3. Sensor 1 refers to the sensor closest to the engine assembly.
  4. Sensor 2 refers to the sensor farthest away from the engine assembly.

CONDITIONING FOR SENSOR TESTING

Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the A/F and HO2 sensors. This is performed in order to heat the sensors sufficiently to obtain the appropriate inspection results.

A093766E23

  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 2,500 rpm and 3,000 rpm for at least 3 minutes (Procedure "C").
  4. While running the engine at 3,000 rpm for 2 seconds and 2,000 rpm for 2 seconds, check the waveforms of the A/F and HO2 sensors using the tester or scan tool (Procedure "D").

NOTICE:
The Air-Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum delay of approximately 20 seconds.

Case
A/F Sensor (Sensor 1)
Output Voltage
HO2 Sensor (Sensor 2)
Output Voltage
Main Suspected Trouble Area
1
Injection Volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
-
Output Voltage
More than 3.35 V
Less than 3.0 V
A107708
Output Voltage
More than 0.55 V
Less than 0.4 V
A103186
2
Injection Volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
  1. A/F sensor
  2. A/F sensor heater
  3. A/F sensor circuit
Output Voltage
Almost
no reaction
A103185
Output Voltage
More than 0.55 V
Less than 0.4 V
A103186
3
Injection Volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
  1. HO2 sensor
  2. HO2 sensor heater
  3. HO2 sensor circuit
Output Voltage
More than 3.35 V
Less than 3.0 V
A107708
Output Voltage
Almost
no reaction
A103185
4
Injection Volume
+25 %
-12.5 %
A103184
Injection Volume
+25 %
-12.5 %
A103184
  1. Fuel pressure
  2. Gas leakage from exhaust system
    (Air-fuel ratio extremely lean or rich)
Output Voltage
Almost
no reaction
A103185
Output Voltage
Almost
no reaction
A103185
  1. Performing "Control the Injection Volume for A/F Sensor" enables technicians to check and graph the output voltages of both the A/F and HO2 sensors.

INSPECTION PROCEDURE

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

  1. Connect the intelligent tester to the DLC3.

  1. Turn the ignition switch to the ON position and turn the tester on.

  1. Enter the following menus: Powertrain / Engine / DTC.

  1. Read the DTCs.

    Result:

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

HINT:
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 (A/F CONTROL)

  1. Connect the intelligent tester to the DLC3.

  1. Start the engine and turn the tester on.

  1. Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.

  1. On the tester, enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.

  1. Perform "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).

  1. Monitor the output voltages of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the tester.

    HINT:
    1. "Control the Injection Volume for A/F Sensor" lowers the fuel injection volume by 12.5 % or increases the injection volume by 25 %.
    2. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

    Tester Display
    (Sensor)
    		Injection Volume
    		Status
    		Voltage
    AFS B1 S1 or AFS B2 S1
    (A/F)
    		+25 %
    		Rich
    		Less than 3.0 V
    AFS B1 S1 or AFS B2 S1
    (A/F)
    		-12.5 %
    		Lean
    		More than 3.35 V
    O2S B1 S2 or O2S B2 S2
    (HO2)
    		+25 %
    		Rich
    		 More than 0.55 V
    O2S B1 S2 or O2S B2 S2
    (HO2)
    		-12.5 %
    		Lean
    		Less than 0.4 V

    Result:

    Status
    AFS B1 S1
    or
    AFS B2 S1
    		Status
    O2S B1 S2
    or
    O2S B2 S2
    		A/F Condition and A/F and
    HO2 Sensor Conditions
    		Misfire
    		Main Suspected Trouble Areas
    		Proceed to
    Lean/Rich
    		Lean/Rich
    		Normal
    		-
    1. Three-Way Catalytic Converter (TWC)
    2. Gas leakage from exhaust system
    		A
    Lean
    		Lean/Rich
    		A/F sensor malfunction
    		-
    1. A/F sensor
    		B
    Rich
    		Lean/Rich
    		A/F sensor malfunction
    		May occur
    1. A/F sensor
    		B
    Lean/Rich
    		Lean
    		HO2 sensor malfunction
    		-
    1. HO2 sensor
    2. Gas leakage from exhaust system
    		C
    Lean/Rich
    		Rich
    		HO2 sensor malfunction
    		-
    1. HO2 sensor
    2. Gas leakage from exhaust system
    		C
    Lean
    		Lean
    		Actual air-fuel ratio lean
    		May occur
    1. Extremely rich or lean actual air-fuel ratio
    2. Gas leakage from exhaust system
    		A
    Rich
    		Rich
    		Actual air-fuel ratio lean
    		-
    1. Extremely rich or lean actual air-fuel ratio
    2. Gas leakage from exhaust system
    		A
    1. Lean:
      1. During "Control the Injection Volume for A/F Sensor", the A/F sensor (AFS) output voltage is consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
    2. Rich:
      1. 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.
    3. Lean/Rich:
      1. During "Control the Injection Volume for A/F Sensor" of the Active Test, the output voltage of the HO2 sensor alternates correctly.


B
CHECK AND REPLACE AIR FUEL RATIO SENSOR

C
CHECK AND REPLACE HEATED OXYGEN SENSOR, AND CHECK AND REPAIR EXHAUST GAS LEAKAGE
A


3.CHECK FOR EXHAUST GAS LEAKS

OK:
No gas leakage.


NG
REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT
OK

REPLACE THREE-WAY CATALYTIC CONVERTER