DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1): 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 DTCs.
   RESULT
   
   

   Result	Proceed to
   P0420	A
   P0420 and other DTCs	B

   HINT: 

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

B → See step   4 

A: Go to next step 

1. Connect the Techstream to the DLC3.
2. Start the engine and warm it up.
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.
6. Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
7. Monitor the voltage outputs of the air fuel ratio sensor and heated oxygen sensor (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.

   HINT: 

   • The Control the Injection Volume for A/F sensor operation lowers the fuel injection volume by 12.5% or increases the injection volume by 25%.
   • Each sensor reacts in accordance with increases and decreases in the fuel injection volume.

     Standard

     Tester Display (Sensor)	Injection Volume	Status	Voltage
     AFS Voltage B1 S1 (A/F)	+25%	Rich	Below 3.1 V
     	-12.5%	Lean	Higher than 3.4 V
     O2S B1 S2 (HO2)	+25%	Rich	Higher than 0.55 V
     	-12.5%	Lean	Below 0.4 V

     RESULT
     
     

     Status AFS Voltage B1 S1	Status O2S B1 S2	A/F Condition and A/F and HO2 Sensors Condition	Misfire	Main Suspected Trouble Area	Proceed to
     Lean/Rich	Lean/Rich	Normal	-	Three-Way Catalytic Converter (TWC) Gas leak from exhaust system	A
     Lean	Lean/Rich	A/F sensor malfunction	-	A/F sensor	B
     Rich	Lean/Rich	A/F sensor malfunction	-	A/F sensor
     Lean/Rich	Lean	HO2 sensor malfunction	-	HO2 sensor Gas leak from exhaust system	C
     Lean/Rich	Rich	HO2 sensor malfunction	-	HO2 sensor Gas leak from exhaust system
     Lean	Lean	Actual air-fuel ratio lean	May occur	Extremely rich or lean actual air-fuel ratio Gas leak from exhaust system	D
     Rich	Rich	Actual air-fuel ratio rich	-	Extremely rich or lean actual air-fuel ratio Gas leak from exhaust system

     Lean: During Control the Injection Volume for A/F sensor, the A/F sensor output voltage (AFS Voltage) is consistently higher than 3.4 V, and the HO2 sensor output voltage (O2S) is consistently below 0.4 V.

     Rich: During Control the Injection Volume for A/F sensor, the AFS Voltage is consistently below 3.1 V, and the O2S is consistently higher than 0.55 V.

     Lean/Rich: During Control the Injection Volume for A/F sensor of the Active Test, the output voltage of the HO2 sensor alternates correctly.

B → See step   5 

C → See step   9 

D → See step   6 

A: Go to next step 

1. Check for exhaust gas leaks.

   OK

   No gas leak.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK: Go to next step 

1. Replace the exhaust manifold converter sub-assembly. Refer to REMOVAL .

NEXT → See step   8 

1. Check for exhaust gas leaks.

   OK

   No gas leak.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK → See step   10