DTC P0420: Catalyst System Efficiency Below Threshold (Bank 1): 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 and ECT / Trouble Codes.
5. Read the DTCs.

   Result

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

   HINT: 

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

B → See step   6 

A: Go to next step 

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. Refer to INSPECTION MODE PROCEDURE .
5. Start the engine.
6. Warm up the engine at an engine speed of 2500 RPM for approximately 90 seconds.
7. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.
8. Perform the Control the Injection Volume operation with the engine in an idling condition.
9. Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.

   HINT: 

   • Change the fuel injection volume within the range of - 12.0% to +12.0%. The injection volume can be changed in fine gradations.
   • 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 there is almost no response from the air fuel ratio sensor, a malfunction of the air fuel ratio sensor is suspected.

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 (Air fuel ratio)	+12%	Rich	Below 3.1 V
   AFS Voltage B1S1 (Air fuel ratio)	-12%	Lean	Higher than 3.4 V
   O2S B1S2 (Heated oxygen)	+12%	Rich	Higher than 0.55 V
   O2S B1S2 (Heated oxygen)	-12%	Lean	Below 0.4 V

   Result

   Status of AFS Voltage B1S1	Status of O2S B1S2	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 alternates correctly.

10. Refer to "Data List / Active Test" [AFS Voltage B1S1, and O2S B1S2]. Refer to DATA LIST / ACTIVE TEST .

B → See step   7 

C → See step   9 

D → See step   11 

A: Go to next step 

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

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK: Go to next step 

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. Refer to INSPECTION MODE PROCEDURE .
5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or more.

   HINT: 

   The A/C switch and all accessory switches should be off.

6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
7. Confirm the Throttle Idle Position is ON and check the engine idling condition and MAP values 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.
   • Do not open the EGR valve 30 steps or more during the Active Test.

   OK

   MAP and idling condition change in response to EGR step position when Throttle Idle Position is ON in Data List.

   Standard

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

   HINT: 

   During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in the EGR valve.

   Result

   Result	Proceed to
   Outside of standard range	A
   Within standard range	B

B → See step   8 

A: Go to next step 

1. Remove the EGR valve assembly. Refer to REMOVAL .
2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

3. Reinstall the EGR valve assembly. Refer to INSTALLATION .

NG → See step   15 

OK → See step   8 

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

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK → See step   10 

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

   OK

   No gas leaks.

NG → REPAIR OR REPLACE EXHAUST GAS LEAK POINT 

OK: Go to next step 

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. Refer to INSPECTION MODE PROCEDURE .
5. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or more.

   HINT: 

   The A/C switch and all accessory switches should be off.

6. Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the EGR Step Position.
7. Confirm the Throttle Idle Position is ON and check the engine idling condition and MAP values 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.
   • Do not open the EGR valve 30 steps or more during the Active Test.

   OK

   MAP and idling condition change in response to EGR step position when Throttle Idle Position is ON in Data List.

   Standard

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

   HINT: 

   During Active Test, if the idling condition does not change in response to EGR step position, then there is probably a malfunction in the EGR valve.

   Result

   Result	Proceed to
   Outside of standard range	A
   Within standard range	B

B → See step   14 

A: Go to next step 

1. Remove the EGR valve assembly. Refer to REMOVAL .
2. Check if the EGR valve is stuck open.

   OK

   EGR valve is tightly closed.

3. Reinstall the EGR valve assembly. Refer to INSTALLATION .

NG → See step   15 

OK → See step   14