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

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 / Trouble Codes.
5. Read the DTCs.

   Result

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

   HINT: 

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

B → See step   4 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Start the engine and warm it up.
3. Turn the Techstream on.
4. Run the engine at an engine speed of 2500 RPM for approximately 90 seconds.
5. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.
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 B1 S1 and O2S B1 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 (Air fuel ratio)	+25%	Rich	Below 3.1 V
     	-12.5%	Lean	Higher than 3.4 V
     O2S B1 S2 (Heated oxygen)	+25%	Rich	Higher than 0.55 V
     	-12.5%	Lean	Below 0.4 V

     Result

     Status AFS Voltage B1 S1	Status O2S B1 S2	Air Fuel Ratio Condition and Air Fuel Ratio and Heated Oxygen Sensors 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 lean actual air fuel ratio Gas leak from exhaust system	D
     Rich	Rich	Actual air fuel ratio rich	-	Extremely rich actual air fuel ratio Gas leak from exhaust system

     Lean: During Control the Injection Volume for A/F Sensor, the air fuel ratio sensor output voltage (AFS Voltage B1 S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1 S2) is consistently below 0.4 V.

     Rich: During Control the Injection Volume for A/F Sensor, the AFS Voltage B1 S1 is consistently below 3.1 V, and the O2S B1 S2 is consistently higher than 0.55 V.

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

B → See step   5 

C → See step   9 

D → See step   11 

A: Go to next step 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK: Go to next step 

1. Replace the front exhaust pipe assembly (TWC: Front catalyst), refer to COMPONENTS .

NEXT → See step   8 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK → See step   10 

1. Check the exhaust gas leaks.

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK → See step   6