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

1. Read the DTCs.

   Powertrain > Engine > Trouble Codes 

   Result

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

   HINT: 

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

Result: 

A 

GO TO DTC CHART 

Result: 

B 

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  30

Result: 

A 

See step  3

1. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher.
2. Warm up the air fuel ratio sensors at an engine speed of 2500 RPM for 90 seconds.
3. Enter the following menus.

   Powertrain > Engine > Active Test 

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

   Data List Display
   Coolant Temperature
   Injection Volume
   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	Higher 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	Higher 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	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)	B
   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	C
   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	D

   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 higher than 0.037 mA, and the air fuel ratio sensor (sensor 2) output current (A/F (O2) Sensor Current B1S2) is consistently higher 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 [09/2024 - ]

Result: 

B 

See step  5

Result: 

C 

See step  6

Result: 

D 

See step  8

Result: 

A 

See step  4

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

See step  29

Result: 

NG 

See step  26

Refer to REMOVAL [09/2024 - ]

HINT: 

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

Refer to INITIALIZATION [09/2022 - ]

Result

Result: 

NEXT 

See step  27

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  26

Result: 

OK 

See step  7

Refer to REMOVAL [09/2022 - ]

HINT: 

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

Refer to INITIALIZATION [09/2022 - ]

Result

Result: 

NEXT 

See step  27

1. Check for exhaust gas leaks.

   OK

   No gas leaks in exhaust system.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

See step  26

Result: 

OK 

See step  9

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Check the PCV hose connections.
2. Check the PCV valve.

   Refer to INSPECTION [09/2022 - ]

   OK

   PCV hose and PCV valve are connected correctly and are not damaged.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE PCV VALVE OR HOSE 

Result: 

OK 

See step  10

1. Check the intake system for vacuum leaks.

   Refer to ON-VEHICLE INSPECTION [09/2022 - ]

   OK

   No leaks in intake system.

   Result

   Proceed to
   OK
   NG

   HINT: 

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

   Refer to INITIALIZATION [09/2022 - ]

Result: 

NG 

REPAIR OR REPLACE INTAKE SYSTEM 

Result: 

OK 

See step  11

1. Read the Data List twice, when the engine is both cold and warmed up.

   Powertrain > Engine > Data List 

   Tester Display
   Coolant Temperature

   Standard

   GTS Display	Condition	Specified Condition
   Coolant Temperature	Cold engine	Same as ambient air temperature
   	Warm engine	Between 75 and 100°C (167 and 212°F)

   Result

   Proceed to
   OK
   NG

   HINT: 

   Perform "Inspection After Repair" after replacing the engine coolant temperature sensor.

   Refer to INITIALIZATION [09/2022 - ]

Result: 

NG 

REPLACE ENGINE COOLANT TEMPERATURE SENSOR 

Refer to REMOVAL [09/2022 - ]

Result: 

OK 

See step  12

Refer to INSPECTION [09/2022 - ]

Result

Result: 

NG 

See step  18

Result: 

OK 

See step  13

Refer to PROCEDURE - Step 2

Result

Result: 

NG 

See step  25

Result: 

OK 

See step  14

Refer to PROCEDURE - Step 3

Result

Result: 

NG 

See step  25

Result: 

OK 

See step  15

Refer to ON-VEHICLE INSPECTION [09/2022 - ]

HINT: 

• If the spark plugs or ignition system malfunctions, engine misfire may occur. The misfire count can be read using the GTS. Enter the following menus: Powertrain / Engine / Data List / Misfire Count Cylinder #1 to Misfire Count Cylinder #3.
• Perform "Inspection After Repair" after repairing or replacing the ignition system.

  Refer to INITIALIZATION [09/2022 - ]

Result

Result: 

NG 

REPAIR OR REPLACE IGNITION SYSTEM 

Result: 

OK 

See step  16

1. Inspect the port fuel injector assembly (whether fuel volume is high or low, and whether injection pattern is poor).

   Refer to INSPECTION [09/2022 - ]

   HINT: 

   Perform "Inspection After Repair" after replacing the port fuel injector assembly.

   Refer to INITIALIZATION [09/2022 - ]

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE PORT FUEL INJECTOR ASSEMBLY 

Refer to REMOVAL [11/2022 - ]

Result: 

OK 

See step  17

Refer to INSPECTION [09/2022 - ]

HINT: 

Perform "Inspection After Repair" after replacing the direct fuel injector assembly.

Refer to INITIALIZATION [09/2022 - ]

Result

Result: 

NG 

REPLACE DIRECT FUEL INJECTOR ASSEMBLY 

Refer to REMOVAL [11/2022 - ]

Result: 

OK 

See step  18

1. Check the connection and terminal contact pressure of connectors and wire harnesses between the mass air flow meter sub-assembly and ECM.

   Refer to ELECTRONIC CIRCUIT INSPECTION PROCEDURE [06/2018 - ]

   HINT: 

   Repair any problems.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  19

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  20

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
   P0420-00 is output	B

Result: 

A 

END 

Result: 

B 

See step  21

1. Disconnect the mass air flow meter sub-assembly connector.
2. Disconnect the ECM connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   C26-3 (VCC) - C142-84 (VCVG)	Always	Below 1 Ω
   C26-1 (FG) - C142-107 (VG)	Always	Below 1 Ω
   C26-2 (E2G) - C142-83 (E2G)	Always	Below 1 Ω
   C26-3 (VCC) or C142-84 (VCVG) - Body ground and other terminals	Always	10 kΩ or higher
   C26-1 (FG) or C142-107 (VG) - Body ground and other terminals	Always	10 kΩ or higher
   C26-2 (E2G) or C142-83 (E2G) - Body ground and other terminals	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  22

Refer to REMOVAL [09/2022 - ]

HINT: 

• If the result of the inspection performed in steps 11 (INSPECT MASS AIR FLOW METER SUB-ASSEMBLY) indicated no problem, proceed to the next step without replacing the mass air flow meter sub-assembly.
• Perform "Inspection After Repair" after replacing the mass air flow meter sub-assembly.

  Refer to INITIALIZATION [09/2022 - ]

Result

Result: 

NEXT 

See step  23

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  24

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
   P0420-00 is output	B

Result: 

A 

END 

Result: 

B 

REPLACE ECM 

Refer to REMOVAL [09/2024 - ]

1. Check the fuel lines for leaks or blockage.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

GO TO FUEL PUMP CONTROL CIRCUIT 

Refer to Fuel Pump Control Circuit [09/2024 - ]

Result: 

NG 

REPAIR OR REPLACE FUEL SYSTEM 

HINT: 

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

Refer to INITIALIZATION [09/2022 - ]

Result

Result: 

NEXT 

See step  27

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  28

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
   P0420-00 is output	B

Result: 

A 

END 

Result: 

B 

See step  29

HINT: 

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

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

   Refer to REMOVAL [09/2022 - ]

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

   Refer to REMOVAL [09/2022 - ]

   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 [09/2022 - ]

Result

Result: 

NG 

REPAIR OR REPLACE EXHAUST SYSTEM 

Result: 

OK 

See step  31

Refer to REMOVAL [09/2022 - ]

HINT: 

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

Refer to INITIALIZATION [09/2022 - ]

Result

Result: 

NEXT 

See step  32

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  33

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