DTC P0420-00: Catalyst System Efficiency Below Threshold Bank 1 [09/2024 - ]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Trouble Codes.
5. 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 [09/2024 - ]

Result: 

A 

See step  2

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in Inspection Mode (Maintenance Mode).

   Refer to INSPECTION MODE PROCEDURE [06/2018 - ]

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

5. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.
6. Idle the engine for 5 minutes or more with park (P) selected.
7. Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / Data List / A/F (O2) Sensor Current B1S1 and O2 Sensor Voltage B1S2.

   Powertrain > Engine > Active Test 

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

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

8. Change the fuel injection volume using the Techstream, and monitor the output voltage of the air fuel ratio sensor (A/F (O2) Sensor Current B1S1) and heated oxygen sensor (O2 Sensor Voltage 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 is displayed as A/F (O2) Sensor Current B1S1, and the heated oxygen sensor is displayed as O2 Sensor Voltage B1S2 on the Techstream.
   • 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
   A/F (O2) Sensor Current B1S1 (Air fuel ratio)	12.5%	Rich	Below -0.075 mA
   	-12.5%	Lean	Higher than 0.037 mA
   O2 Sensor Voltage B1S2 (Heated oxygen)	12.5%	Rich	Higher than 0.55 V
   	-12.5%	Lean	Below 0.4 V

   Result

   Status A/F (O2) Sensor Current B1S1	Status O2 Sensor Voltage 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 EGR valve assembly	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 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: While performing the Active Test "Control the Injection Volume for A/F Sensor", the air fuel ratio sensor output voltage (A/F (O2) Sensor Current B1S1) is consistently higher than 0.037 mA, and the heated oxygen sensor output voltage (O2 Sensor Voltage 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 (A/F (O2) Sensor Current B1S1) is consistently below -0.075 mA, and the heated oxygen sensor output voltage (O2 Sensor Voltage 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 (A/F (O2) Sensor Current B1S1) or heated oxygen sensor (O2 Sensor Voltage B1S2) alternates correctly.

Result: 

B 

See step  6

Result: 

C 

See step  7

Result: 

D 

See step  9

Result: 

A 

See step  3

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  13

Result: 

OK 

See step  4

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in Inspection Mode (Maintenance Mode).

   Refer to INSPECTION MODE PROCEDURE [06/2018 - ]

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

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

   HINT: 

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

6. Enter the following menus: Powertrain / Engine / Active Test / Control the EGR Step Position / Data List / Intake Manifold Absolute Pressure and Engine Independent.

   Powertrain > Engine > Active Test 

   Active Test Display
   Control the EGR Step Position

   Data List Display
   Intake Manifold Absolute Pressure
   Engine Independent

7. 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.
   NOTE:

   • 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  16

Result: 

NG 

See step  5

1. Remove the EGR valve assembly.

   Refer to REMOVAL [11/2022 - ]

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 [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  16

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

Refer to REMOVAL [11/2022 - ]

1. Replace the air fuel ratio sensor.

   Refer to REMOVAL [01/2019 - ]

   HINT: 

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

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  14

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  13

Result: 

OK 

See step  8

1. Replace the heated oxygen sensor.

   Refer to REMOVAL [01/2019 - ]

   HINT: 

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

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  14

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  13

Result: 

OK 

See step  10

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Put the engine in Inspection Mode (Maintenance Mode).

   Refer to INSPECTION MODE PROCEDURE [06/2018 - ]

   Powertrain > Hybrid Control > Utility 

   Tester Display
   Inspection Mode

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

   HINT: 

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

6. Enter the following menus: Powertrain / Engine / Active Test / Control the EGR Step Position / Data List / Intake Manifold Absolute Pressure and Engine Independent.

   Powertrain > Engine > Active Test 

   Active Test Display
   Control the EGR Step Position

   Data List Display
   Intake Manifold Absolute Pressure
   Engine Independent

7. 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.
   NOTE:

   • 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  12

Result: 

NG 

See step  11

1. Remove the EGR valve assembly.

   Refer to REMOVAL [11/2022 - ]

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 [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

Refer to REMOVAL [11/2022 - ]

Result: 

OK 

See step  12

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 [09/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  14

1. Repair or replace exhaust system.

   HINT: 

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

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  14

1. Connect the Techstream to the DLC3.
2. Turn the power switch on (IG).
3. Turn the Techstream on.
4. Clear the DTCs.

   Powertrain > Engine > Clear DTCs 

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

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  15

1. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
2. Enter the following menus: Powertrain / Engine / Trouble Codes.
3. 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  16

HINT: 

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

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

   Refer to COMPONENTS [09/2022 - ]

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

   Refer to COMPONENTS [01/2019 - ]

   Result

   Proceed to
   NEXT

Result: 

NEXT 

END