DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1); DTC P0430: Catalyst System Efficiency Below Threshold (Bank 2): Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream on.
3. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
4. Read DTCs.
   RESULT
   
   

   Result	Proceed to
   P0420 or P0430 is output	A
   P0420 or P0430 and other DTCs are output	B

   HINT: 

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

B → See step   13 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Start the engine and turn the Techstream on.
3. Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
4. Enter the following menus: 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 12.5 or -12.5 button to change the fuel injection volume).
6. Monitor the voltage outputs of the A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

   HINT: 

   • 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 A/F 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.

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 or AFS Voltage B2S1 (A/F)	12.5%	Rich	Less than 3.1 V
   AFS Voltage B1S1 or AFS Voltage B2S1 (A/F)	-12.5%	Lean	More than 3.4 V
   O2S B1S2 or O2S B2S2 (HO2)	12.5%	Rich	More than 0.55 V
   O2S B1S2 or O2S B2S2 (HO2)	-12.5%	Lean	Less than 0.4 V

   RESULT
   
   

   Status AFS Voltage B1S1 or AFS Voltage B2S1	Status O2S B1S2 or O2S B2S2	A/F Condition and A/F and HO2 Sensor Condition	Misfire	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	Three-Way Catalytic Converter (TWC) Gas leak from exhaust system	A
   Lean	Lean/Rich	A/F sensor malfunction	-	A/F sensor	B
   Rich	Lean/Rich	A/F sensor malfunction	-	A/F sensor
   Lean/Rich	Lean	HO2 sensor malfunction	-	HO2 sensor Gas leak from exhaust system	C
   Lean/Rich	Rich	HO2 sensor malfunction	-	HO2 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 for A/F Sensor, the A/F sensor output voltage (AFS) is consistently more than 3.4 V, and the HO2 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 3.1 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 A/F sensor and HO2 sensor alternates correctly.

B → See step   7 

C → See step   5 

D → See step   6 

A: Go to next step 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

NG → See step   8 

OK: Go to next step 

HINT: 

Confirm the replacement parts, referring to the illustration in the Catalyst Location.

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
5. Read DTCs.
   RESULT
   
   

   Result	Proceed to
   P0420 is output	A, B
   P0430 is output	C, D
   P0420 and P0430 are output	A, B, C, D

A → See step   16 

B → See step   14 

C → See step   17 

D → See step   15 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

OK → See step   9 

NG → See step   8 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

OK → See step   10 

NG → See step   8 

1. Replace the air fuel ratio sensor. Refer to REMOVAL .

   HINT: 

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

NEXT → See step   11 

1. Repair or replace exhaust gas leak point.

   HINT: 

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

NEXT → See step   11 

1. Replace the heated oxygen sensor. Refer to REMOVAL .

   HINT: 

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

NEXT → See step   11 

1. Check the cause of extremely rich or lean actual air fuel ratio, referring to the DTC P0171 Inspection Procedure. Refer to INSPECTION PROCEDURE .

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Clear the DTCs. Refer to DTC CHECK / CLEAR .
5. Turn the ignition switch off and wait for at least 30 seconds.
6. Start the engine.
7. Turn the tester on.
8. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
9. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
10. Read pending DTCs.
    RESULT
    
    

    Result	Proceed to
    DTC P0420 and/or P0430 is output	A
    DTC is not output	B

B → END 

A: Go to next step 

HINT: 

Confirm the replacement parts, referring to the illustration in the Catalyst Location.

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
5. Read DTCs.
   RESULT
   
   

   Result	Proceed to
   P0420 is output	A, B
   P0430 is output	C, D
   P0420 and P0430 are output	A, B, C, D

A → See step   16 

B → See step   14 

C → See step   17 

D → See step   15