DTC P0420-00: Catalyst System Efficiency Below Threshold Bank 1 [11/2023 - ]: Procedure

1. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTC P0420-00 is output	A
   DTC P0420-00 and other DTCs are output	B

   HINT: 

   If any DTCs other than P0420-00 are output, troubleshoot those DTCs first.

Result: 

B 

GO TO DTC CHART  . Refer to DIAGNOSTIC TROUBLE CODE CHART [11/2023 - 11/2024] , or refer to DIAGNOSTIC TROUBLE CODE CHART [11/2024 - ]

Result: 

A 

See step  2

1. Using the GTS, read the value displayed in the Freeze Frame Data.

   Powertrain > Engine > DTC (P0420-00) > Freeze Frame Data 

   Tester Display
   Long FT B1S2

   Result

   GTS Display	Result	Proceed to
   Long FT B1S2	Less than 1.0%	A
   	1.0% or higher	B

Result: 

B 

See step  18

Result: 

A 

See step  3

1. Put the engine in Inspection Mode (Maintenance Mode).

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

2. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.

   Powertrain > Engine > Data List 

   Tester Display
   Coolant Temperature

3. Idle the engine for 5 minutes or more with the shift lever in P.
4. Change the fuel injection volume using the GTS, and monitor the output current of the air fuel ratio sensor (sensor 1) (A/F (O2) Sensor Current B1S1) and air fuel ratio sensor (sensor 2) (A/F (O2) Sensor Current B1S2) displayed on the GTS.

   Powertrain > Engine > Active Test 

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

   Data List Display
   A/F (O2) Sensor Current B1S1
   A/F (O2) Sensor Current B1S2

   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 (sensor 1) is displayed as A/F (O2) Sensor Current B1S1, and the air fuel ratio sensor (sensor 2) is displayed as A/F (O2) Sensor Current B1S2 on the GTS.
   • The air fuel ratio sensor (sensor 1) has an output delay of a few seconds and the air fuel ratio sensor (sensor 2) has a maximum output delay of approximately 20 seconds.
   • If the sensor output current does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.

   Standard

   GTS Display (Sensor)	Injection Volume	Status	Current
   A/F (O2) Sensor Current B1S1 (Air fuel ratio (sensor 1))	12.5%	Rich	Below -0.075 mA
   	-12.5%	Lean	More than 0.037 mA
   A/F (O2) Sensor Current B1S2 (Air fuel ratio (sensor 2))	12.5%	Rich	Below -0.86 mA
   	-12.5%	Lean	More than 0.33 mA

   Result

   Status A/F (O2) Sensor Current B1S1	Status A/F (O2) Sensor Current B1S2	Actual air fuel ratio, air fuel ratio sensor (sensor 1) and air fuel ratio sensor (sensor 2) condition	Main Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	Three-way catalytic converter Gas leak from exhaust system EGR valve assembly	A
   Lean	Lean/Rich	Air fuel ratio sensor (sensor 1) malfunction	Air fuel ratio sensor (sensor 1)	B
   Rich	Lean/Rich	Air fuel ratio sensor (sensor 1) malfunction	Air fuel ratio sensor (sensor 1)
   Lean/Rich	Lean	Air fuel ratio sensor (sensor 2) malfunction	Air fuel ratio sensor (sensor 2) Gas leak from exhaust system	C
   Lean/Rich	Rich	Air fuel ratio sensor (sensor 2) malfunction	Air fuel ratio sensor (sensor 2) Gas leak from exhaust system
   Lean	Lean	Actual air fuel ratio lean	Extremely lean actual air fuel ratio Gas leak from exhaust system EGR valve assembly	D
   Rich	Rich	Actual air fuel ratio rich	Extremely rich actual air fuel ratio Gas leak from exhaust system EGR valve assembly

   1. Lean: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor (sensor 1) output current (A/F (O2) Sensor Current B1S1) is consistently more than 0.037 mA, and the air fuel ratio sensor (sensor 2) output current (A/F (O2) Sensor Current B1S2) is consistently more than 0.33 mA.
   2. Rich: During the Control the Injection Volume for A/F Sensor Active Test, the air fuel ratio sensor (sensor 1) output current (A/F (O2) Sensor Current B1S1) is consistently below -0.075 mA, and the air fuel ratio sensor (sensor 2) output current (A/F (O2) Sensor Current B1S2) is consistently below -0.86 mA.
   3. Lean/Rich: During the Control the Injection Volume for A/F Sensor Active Test, the output current of the air fuel ratio sensor (sensor 1) or air fuel ratio sensor (sensor 2) alternate correctly.

   HINT: 

   Refer to "Data List / Active Test" [A/F (O2) Sensor Current B1S1, A/F (O2) Sensor Current B1S2].

   Refer to DATA LIST / ACTIVE TEST [11/2023 - 11/2024] , or refer to DATA LIST / ACTIVE TEST [11/2024 - ]

Result: 

B 

See step  7

Result: 

C 

See step  8

Result: 

D 

See step  10

Result: 

A 

See step  4

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  14

Result: 

OK 

See step  5

1. Put the engine in Inspection Mode (Maintenance Mode).

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

2. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.

   Powertrain > Engine > Data List 

   Tester Display
   Coolant Temperature

   HINT: 

   The A/C switch and all accessories should be off.

3. Confirm that the value of Data List item Engine Independent is "Operate" then check the value of Intake Manifold Absolute Pressure while performing the Active Test.

   Powertrain > Engine > Active Test 

   Active Test Display
   Control the EGR Step Position

   Data List Display
   Intake Manifold Absolute Pressure
   Engine Independent

   NOTE:

   • Make sure that the value of Data List item Engine Independent is "Operate" while performing the Active Test.
   • Do not leave the EGR valve open for 10 seconds or more during the Active Test.
   • Be sure to return the EGR valve to step 0 when the Active Test is completed.
   • Do not open the EGR valve 30 steps or more during the Active Test.

   OK

   The value of Intake Manifold Absolute Pressure changes in response to the EGR step position when the value of Engine Independent is "Operate".

   Standard

   -	Control the EGR Step Position (Active Test)
   	0 Steps	0 to 30 Steps
   Intake Manifold Absolute Pressure (Data List)	(EGR valve is fully closed)	Intake Manifold Absolute Pressure value is at least +10 kPa (1.45 psi) higher than when EGR valve is fully closed

   HINT: 

   • If the value of Data List item Engine Independent is "Not Opr" when the engine is idling, charge control is being performed. Perform the Active Test after charge control is complete ("Operate" is displayed).
   • While performing the Active Test, if the increase in the value of Intake Manifold Absolute Pressure is small, the EGR valve assembly may be malfunctioning.
   • Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of Intake Manifold Absolute Pressure may occur while performing the Active Test. However, the amount that the value of Intake Manifold Absolute Pressure increases will be smaller than normal.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  17

Result: 

NG 

See step  6

1. Remove the EGR valve assembly.

   Refer to REMOVAL [11/2023 - ]

2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

   HINT: 

   Perform "Inspection After Repair" after replacing the EGR valve assembly.

   Refer to INITIALIZATION [10/2021 - ]

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  17

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

Refer to REMOVAL [11/2023 - ]

Refer to REMOVAL [12/2019 - ]

HINT: 

Perform "Inspection After Repair" after replacing the air fuel ratio sensor (sensor 1).

Refer to INITIALIZATION [10/2021 - ]

Result

Result: 

NEXT 

See step  15

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  14

Result: 

OK 

See step  9

Refer to REMOVAL [12/2019 - ]

HINT: 

Perform "Inspection After Repair" after replacing the air fuel ratio sensor (sensor 2).

Refer to INITIALIZATION [10/2021 - ]

Result

Result: 

NEXT 

See step  15

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  14

Result: 

OK 

See step  11

1. Put the engine in Inspection Mode (Maintenance Mode).

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

2. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.

   Powertrain > Engine > Data List 

   Tester Display
   Coolant Temperature

   HINT: 

   The A/C switch and all accessories should be off.

3. Confirm that the value of Data List item Engine Independent is "Operate" then check the value of Intake Manifold Absolute Pressure while performing the Active Test.

   Powertrain > Engine > Active Test 

   Active Test Display
   Control the EGR Step Position

   Data List Display
   Intake Manifold Absolute Pressure
   Engine Independent

   NOTE:

   • Make sure that the value of Data List item Engine Independent is "Operate" while performing the Active Test.
   • Do not leave the EGR valve open for 10 seconds or more during the Active Test.
   • Be sure to return the EGR valve to step 0 when the Active Test is completed.
   • Do not open the EGR valve 30 steps or more during the Active Test.

   OK

   The value of Intake Manifold Absolute Pressure changes in response to the EGR step position when the value of Engine Independent is "Operate".

   Standard

   -	Control the EGR Step Position (Active Test)
   	0 Steps	0 to 30 Steps
   Intake Manifold Absolute Pressure (Data List)	(EGR valve is fully closed)	Intake Manifold Absolute Pressure value is at least +10 kPa (1.45 psi) higher than when EGR valve is fully closed

   HINT: 

   • If the value of Data List item Engine Independent is "Not Opr" when the engine is idling, charge control is being performed. Perform the Active Test after charge control is complete ("Operate" is displayed).
   • While performing the Active Test, if the increase in the value of Intake Manifold Absolute Pressure is small, the EGR valve assembly may be malfunctioning.
   • Even if the EGR valve assembly is malfunctioning, rough idling or an increase in the value of Intake Manifold Absolute Pressure may occur while performing the Active Test. However, the amount that the value of Intake Manifold Absolute Pressure increases will be smaller than normal.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  13

Result: 

NG 

See step  12

1. Remove the EGR valve assembly.

   Refer to REMOVAL [11/2023 - ]

2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

   HINT: 

   Perform "Inspection After Repair" after replacing the EGR valve assembly.

   Refer to INITIALIZATION [10/2021 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

Refer to REMOVAL [11/2023 - ]

Result: 

OK 

See step  13

1. Check the cause of extremely rich or lean actual air fuel ratio, referring to the DTC P0171-00 and P0172-00 Inspection Procedure.

   Refer to DTC P0171-00: System Too Lean Bank 1; DTC P0172-00: System Too Rich Bank 1; DTC P1170-00: Fuel Performance/Port Injector; DTC P117B-00: Fuel Performance/Direct Injector [11/2023 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  15

1. Repair or replace exhaust system.

   HINT: 

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

   Refer to INITIALIZATION [10/2021 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  15

1. Clear the DTCs.

   Powertrain > Engine > Clear DTCs 

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

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  16

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   Result	Proceed to
   DTCs are not output	A
   DTC P0420-00 is output	B

Result: 

A 

END 

Result: 

B 

See step  17

HINT: 

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

1. Replace the exhaust manifold (TWC: Front catalyst).

   Refer to REMOVAL [10/2022 - ]

2. Replace the front exhaust pipe assembly (TWC: Rear catalyst).

   Refer to REMOVAL [10/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

END 

OK

No gas leaks in exhaust system.

HINT: 

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

Refer to INITIALIZATION [10/2021 - ]

Result

Result: 

NG 

REPAIR OR REPLACE EXHAUST SYSTEM 

Result: 

OK 

See step  19

Refer to REMOVAL [12/2019 - ]

HINT: 

Perform "Inspection After Repair" after replacing the air fuel ratio sensor (sensor 2).

Refer to INITIALIZATION [10/2021 - ]

Result

Result: 

NEXT 

See step  20

1. Clear the DTCs.

   Powertrain > Engine > Clear DTCs 

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

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  21

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Check for DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

   DTCs are not output.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

END