DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1) [03/2019 - 11/2022]: 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 and ECT / Trouble Codes.
5. Read the DTCs.

   Powertrain > Engine and ECT > Trouble Codes 

   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 [03/2019 - 04/2020] , or refer to DIAGNOSTIC TROUBLE CODE CHART [04/2020 - 09/2022] , or refer to DIAGNOSTIC TROUBLE CODE CHART [09/2022 - 11/2022]

Result: 

A 

See step  2

1. Connect the Techstream to the DLC3.
2. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.
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 and ECT / Active Test / Control the Injection Volume for A/F Sensor / Data List / Coolant Temp, AFS Voltage B1S1 and O2S B1S2.

   Powertrain > Engine and ECT > Active Test 

   Active Test Display
   Control the Injection Volume for A/F Sensor

   Data List Display
   Coolant Temp
   AFS Voltage B1S1
   O2S B1S2

6. Change the fuel injection volume using the Techstream, and monitor the output voltage of the air fuel ratio sensor (AFS Voltage B1S1) and heated oxygen sensor (O2S B1S2) displayed on the Techstream.

   HINT: 

   • The Active Test "Control the Injection Volume for A/F Sensor" can be used to lower the fuel injection volume by 12.5% or increase the injection volume by 12.5%.
   • 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)	12.5%	Rich	Below 3.1 V
   	-12.5%	Lean	Higher than 3.4 V
   O2S B1S2 (Heated oxygen)	12.5%	Rich	Higher than 0.55 V
   	-12.5%	Lean	Below 0.4 V

   Result

   Status AFS Voltage B1S1	Status O2S B1S2	Actual air fuel ratio, air fuel ratio sensor and heated oxygen sensor condition	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	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

   1. Lean: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.
   2. Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently below 3.1 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently higher than 0.55 V.
   3. Lean/Rich: While performing the Active Test "Control the Injection Volume for A/F Sensor", the output voltage of the fuel ratio sensor (AFS Voltage B1S1) or heated oxygen sensor (O2S B1S2) alternates correctly.

   HINT: 

   Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2].

   Refer to DATA LIST / ACTIVE TEST [03/2019 - 04/2020] , or refer to DATA LIST / ACTIVE TEST [04/2020 - 11/2022]

Result: 

B 

See step  4

Result: 

C 

See step  5

Result: 

D 

See step  7

Result: 

A 

See step  3

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  12

Result: 

NG 

See step  9

1. Replace the air fuel ratio sensor.

   Refer to REMOVAL [01/2019 - 11/2022]

   HINT: 

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

   Refer to INITIALIZATION [01/2019 - 11/2022]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  10

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  9

Result: 

OK 

See step  6

1. Replace the heated oxygen sensor.

   Refer to REMOVAL [01/2019 - 11/2022]

   HINT: 

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

   Refer to INITIALIZATION [01/2019 - 11/2022]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  10

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  9

Result: 

OK 

See step  8

1. Check the cause of extremely rich or lean actual air fuel ratio, referring to the DTC P0171 and P0172 Inspection Procedure.

   Refer to DTC P0171: System Too Lean (Bank 1); DTC P0172: System Too Rich (Bank 1) [03/2019 - 11/2022]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  10

1. Repair or replace exhaust gas leak point.

   HINT: 

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

   Refer to INITIALIZATION [01/2019 - 11/2022]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  10

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Clear the DTCs.

   Powertrain > Engine and ECT > Clear DTCs 

5. Turn the ignition switch off and wait for at least 30 seconds.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  11

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
3. Read the DTCs.

   Powertrain > Engine and ECT > Trouble Codes 

   Result

   Result	Proceed to
   DTCs are not output	A
   DTC P0420 is output	B

Result: 

A 

END 

Result: 

B 

See step  12

HINT: 

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

1. Replace the front exhaust pipe assembly (TWC: Front and rear catalyst).

   Refer to COMPONENTS [01/2019 - 11/2022]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

END