DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1); DTC P0430: Catalyst System Efficiency Below Threshold (Bank 2) [08/2015 - 08/2022]: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the engine switch on (IG).
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
5. Read the DTCs.
   RESULT
   
   

   Result	Proceed to
   P0420 or P0430 is output	A
   P0420 or P0430 and other DTCs are output	B

   HINT: 

   If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.

Result: 

B 

GO TO DTC CHART 

(Refer to DIAGNOSTIC TROUBLE CODE CHART [08/2015 - 08/2016] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2016 - 08/2017] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2017 - 08/2019] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2019 - 08/2020] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2020 - 08/2021] , or refer to DIAGNOSTIC TROUBLE CODE CHART [08/2021 - 08/2022] )

Result: 

A 

See step  2

1. Connect the Techstream to the DLC3.
2. Start the engine.
3. Turn the Techstream on.
4. Warm up the engine and 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.
6. Perform the Control the Injection Volume for A/F Sensor operation with the engine idling.
7. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2) displayed on the Techstream.

   HINT: 

   • Change the fuel injection volume within the range of - 12.5% to +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.

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio)	+12.5%	Rich	Below 3.1 V
   AFS Voltage B1S1 or AFS Voltage B2S1 (Air fuel ratio)	-12.5%	Lean	Higher than 3.4 V
   O2S B1S2 or O2S B2S2 (Heated oxygen)	+12.5%	Rich	Higher than 0.55 V
   O2S B1S2 or O2S B2S2 (Heated oxygen)	-12.5%	Lean	Below 0.4 V

   RESULT
   
   

   Status of AFS Voltage B1S1 or AFS Voltage B2S1	Status of O2S B1S2 or O2S B2S2	Air Fuel Ratio Condition and Air Fuel Ratio and Heated Oxygen Sensor Condition	Misfire	Suspected Trouble Area	Proceed to
   Lean/Rich	Lean/Rich	Normal	-	Three-way catalytic converter Gas leaks 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	B
   Lean/Rich	Lean	Heated oxygen sensor malfunction	-	Heated oxygen sensor Gas leaks from exhaust system	C
   Lean/Rich	Rich	Heated oxygen sensor malfunction	-	Heated oxygen sensor Gas leaks from exhaust system	C
   Lean	Lean	Actual air fuel ratio lean	May occur	Extremely rich or lean actual air fuel ratio Gas leaks from exhaust system EGR valve assembly	D
   Rich	Rich	Actual air fuel ratio rich	-	Extremely rich or lean actual air fuel ratio Gas leaks from exhaust system EGR valve assembly	D

   Lean: During the Control the Injection Volume Active Test, the air fuel ratio sensor output voltage (AFS Voltage) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S) is consistently below 0.4 V.

   Rich: During the Control the Injection Volume Active Test, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.

   Lean/Rich: During the Control the Injection Volume Active Test, the output voltage of the air fuel ratio sensor and heated oxygen sensor alternate correctly.

8. Refer to "Data List / Active Test" [AFS Voltage B1S1, AFS Voltage B2S1, O2S B1S2 and O2S B2S2] (Refer to DATA LIST / ACTIVE TEST [08/2015 - 08/2018] , or refer to DATA LIST / ACTIVE TEST [08/2018 - 08/2019] , or refer to DATA LIST / ACTIVE TEST [08/2019 - ] ).

   HINT: 

   Perform "Inspection After Repair" after replacing the air fuel ratio sensor (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

B 

REPLACE AIR FUEL RATIO SENSOR 

(Refer to REMOVAL [08/2015 - ] )

Result: 

C 

See step  7

Result: 

D 

See step  8

Result: 

A 

See step  3

1. Inspect for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipes.

   OK

   No gas leaks.

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the exhaust system (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

Result: 

OK 

See step  4

1. Connect the Techstream to the DLC3.
2. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

   HINT: 

   • When performing the Active Test, make sure the shift lever is in P or N.
   • The A/C switch and all accessory switches should be off.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
5. Confirm that Throttle Idle Position is ON and check the engine idling condition and the value of MAP in the Data List while performing the Active Test.

   HINT: 

   • 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.

   OK

   MAP and idling condition change in response to EGR step position as follows.

   Standard

   -	EGR Step Position (Active Test)
   	Step 0	Step 0 to 30
   Idling condition	Steady idling	Idling changes from steady to rough idling or engine stalls
   MAP (Data List)	20 to 40 kPa (150 to 300 mmHg)	MAP value is at least 10 kPa (75 mmHg) higher than when EGR valve is fully closed

Result: 

OK 

See step  6

Result: 

NG 

See step  5

1. Remove the EGR valve assembly (Refer to REMOVAL [08/2015 - ] ).
2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

   HINT: 

   Perform "Inspection After Repairs" after replacing the EGR valve assembly (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

(Refer to REMOVAL [08/2015 - ] )

Result: 

OK 

See step  6

1. According to the DTCs output above (Check for Any Other DTCs Output), proceed to the next step referring to the table below.
   RESULT
   
   

   Result	Proceed to
   P0420 is output	A
   P0430 is output	B
   P0420 and P0430 are output	A and B

Result: 

A 

REPLACE EXHAUST MANIFOLD ASSEMBLY LH AND FRONT NO. 2 EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST) 

(Refer to REMOVAL [08/2015 - ] )

Result: 

B 

REPLACE EXHAUST MANIFOLD ASSEMBLY RH AND FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST) 

(Refer to REMOVAL [08/2015 - ] )

1. Inspect for exhaust gas leaks from the exhaust manifold assembly and exhaust pipes.

   OK

   No gas leaks.

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the exhaust system or heated oxygen sensor (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

OK 

REPLACE HEATED OXYGEN SENSOR 

(Refer to REMOVAL [08/2015 - ] )

Result: 

NG 

REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

1. Inspect for exhaust gas leaks from the exhaust manifold assembly and exhaust pipes.

   OK

   No gas leaks.

   HINT: 

   Perform "Inspection After Repair" after repairing or replacing the exhaust system (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

NG 

REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

Result: 

OK 

See step  9

1. Connect the Techstream to the DLC3.
2. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.

   HINT: 

   • When performing the Active Test, make sure the shift lever is in P or N.
   • The A/C switch and all accessory switches should be off.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
5. Confirm that Throttle Idle Position is ON and check the engine idling condition and the value of MAP in the Data List while performing the Active Test.

   HINT: 

   • 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.

   OK

   MAP and idling condition change in response to EGR step position as follows.

   Standard

   -	EGR Step Position (Active Test)
   	Step 0	Step 0 to 30
   Idling condition	Steady idling	Idling changes from steady to rough idling or engine stalls
   MAP (Data List)	20 to 40 kPa (150 to 300 mmHg)	MAP value is at least 10 kPa (75 mmHg) higher than when EGR valve is fully closed

Result: 

OK 

CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO 

Result: 

NG 

See step  10

1. Remove the EGR valve assembly (Refer to REMOVAL [08/2015 - ] ).
2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

   HINT: 

   Perform "Inspection After Repairs" after replacing the EGR valve assembly (Refer to INITIALIZATION [08/2015 - ] ).

Result: 

OK 

CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO 

Result: 

NG 

REPLACE EGR VALVE ASSEMBLY 

(Refer to REMOVAL [08/2015 - ] )