DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) [06/2016 - 07/2018]: 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.

Result: 

B 

GO TO DTC CHART 

(Refer to DIAGNOSTIC TROUBLE CODE CHART [06/2016 - 03/2017] , or refer to DIAGNOSTIC TROUBLE CODE CHART [03/2017 - 07/2018] )

Result: 

A 

See step  2

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
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 B1S1 and O2S B1S2) displayed on the Techstream.

   HINT: 

   • Change the fuel injection volume within the range of - 12% to +12%.
   • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
   • 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.
   • If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

   Standard

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 (Air fuel ratio)	+12%	Rich	Below 2.0 V
   	-12%	Lean	Higher than 2.4 V
   O2S B1S2 (Heated oxygen)	+12%	Rich	Higher than 0.55 V
   	-12%	Lean	Below 0.4 V

   Result

   Status AFS Voltage B1S1	Status O2S B1S2	A/F Condition and A/F and HO2 Sensor Conditions	Misfire	Main Suspected Trouble Areas	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	Three-Way Catalytic Converter (TWC) 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
   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
   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 air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 2.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.

   Rich: During Control the Injection Volume for A/F Sensor, the AFS Voltage B1S1 is consistently below 2.0 V, and the O2S B1S2 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 air fuel ratio sensor and heated oxygen sensor alternate correctly.

Result: 

B 

REPLACE AIR FUEL RATIO SENSOR 

(Refer to REMOVAL [06/2016 - ] )

Result: 

C 

See step  5

Result: 

D 

See step  6

Result: 

A 

See step  3

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

Result: 

NG 

REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

Result: 

OK 

See step  4

1. Replace the exhaust manifold (TWC: front catalyst) (Refer to REMOVAL [06/2016 - ] ).

Result: 

NEXT 

REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST) 

(Refer to REMOVAL [06/2016 - ] )

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

Result: 

OK 

REPLACE HEATED OXYGEN SENSOR 

(Refer to REMOVAL [06/2016 - ] )

Result: 

NG 

REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

1. Check for exhaust gas leaks.

   OK

   No gas leaks.

Result: 

OK 

CHECK CAUSE OF EXTREMELY RICH OR LEARN ACTUAL AIR FUEL RATIO 

(Refer to CAUTION / NOTICE / HINT )

Result: 

NG 

REPAIR OR REPLACE EXHAUST GAS LEAK POINT