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 engine switch on (IG) and turn the Techstream on.
3. Select the following menu items: Powertrain/Engine/Trouble Codes.
4. Read 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 

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. Select the following menu items: Powertrain/Engine/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 A/F and HO2 sensors (AFS Voltage 0B1 S1 and O2S B1 S2 or AFS Voltage B2 S1 and O2S B2 S2) 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 25%.
   • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

     Standard

     Techstream Display (Sensor)	Injection Volume	Status	Voltage
     AFS Voltage B1 S1 or AFS Voltage B2 S1 (A/F)	+25%	Rich	Less than 3.1 V
     AFS Voltage B1 S1 or AFS Voltage B2 S1 (A/F)	-12.5%	Lean	More than 3.4 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 Voltage B1 S1 or AFS Voltage B2 S1	Status O2S B1 S2 or O2S B2 S2	A/F Condition and A/F and HO2 Sensor Condition	Misfire	Main Suspected Trouble Area	Proceed to
     Lean/Rich	Lean/Rich	Normal	-	Three-Way Catalytic Converter (TWC) Gas leakage 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 leakage from exhaust system	C
     Lean/Rich	Rich	HO2 sensor malfunction	-	HO2 sensor Gas leakage from exhaust system
     Lean	Lean	Actual air-fuel ratio lean	May occur	Extremely rich or lean actual air-fuel ratio Gas leakage from exhaust system	D
     Rich	Rich	Actual air-fuel ratio rich	-	Extremely rich or lean actual air-fuel ratio Gas leakage 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 HO2 sensor alternates correctly.

D → See step   7 

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

B → CHECK AND REPLACE AIR FUEL RATIO SENSOR 

A: Go to next step 

OK

No gas leakage.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK: Go to next step 

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG) and turn the Techstream on.
3. Enter the following menus: Powertrain/Engine/Trouble Codes/Pending.
4. Read the pending DTCs.

   Result

   Display (DTC output)	Proceed to
   P0420	A
   P0430	B
   P0420 and P0430	A and B

B → See step   6 

A: Go to next step 

1. Replace the exhaust manifold sub-assembly RH (TWC: Front catalyst). Refer COMPONENTS .

NEXT → See step   8 

1. Replace the exhaust manifold sub-assembly LH (TWC: Front catalyst). Refer COMPONENTS .

NEXT → See step   8 

1. Inspect for exhaust gas leaks from the exhaust manifold and exhaust pipes.

   OK

   No gas leaks

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK → CHECK ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO