Dtc P0420 Catalyst System Efficiency Below Threshold (Bank 1)

MONITOR DESCRIPTION

CATALYST LOCATION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

MONITOR RESULT

CONFIRMATION DRIVING PATTERN

CONDITIONING FOR SENSOR TESTING

INSPECTION PROCEDURE

CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420)

PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME)

CHECK FOR EXHAUST GAS LEAK

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

REPLACE AIR-FUEL RATIO SENSOR (BANK 1 SENSOR 1)

CHECK FOR EXHAUST GAS LEAK

REPLACE HEATED OXYGEN SENSOR (BANK 1 SENSOR 2)

CHECK FOR EXHAUST GAS LEAK

CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO

REPAIR OR REPLACE EXHAUST GAS LEAK POINT

CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)

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

MONITOR DESCRIPTION

CATALYST LOCATION

MONITOR STRATEGY

TYPICAL ENABLING CONDITIONS

TYPICAL MALFUNCTION THRESHOLDS

MONITOR RESULT

CONFIRMATION DRIVING PATTERN

HINT:

Performing this confirmation driving pattern will activate the catalyst efficiency monitor. This is very useful for verifying the completion of a repair.

1. Connect the Techstream to the DLC3.
   
2. Turn the ignition switch to ON.
   
3. Turn the Techstream on.
   
4. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation).
   
5. Turn the ignition switch off and wait for at least 30 seconds.
   
6. Turn the ignition switch to ON and turn the Techstream on.
   
7. Enter the following menus: Powertrain / Engine and ECT / Monitor / Current Monitor.
   
8. Check that Catalyst Efficiency / Current is Incomplete.
   
9. Start the engine and warm it up until the engine coolant temperature is 75°C (167°F) or higher [A].
   
10. Drive the vehicle at approximately 60 km/h (38 mph) for 10 minutes or more [B].
    

    NOTICE:

    When performing the confirmation driving pattern, obey all speed limits and traffic laws.

    HINT:

    1. Drive the vehicle while keeping the engine load as constant as possible.
       
    2. The monitor item will change to Complete as the catalyst efficiency monitor operates [C].
       
11. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    
12. Check if any DTCs (pending DTCs) are stored.
    

    HINT:

    If the monitor does not change to Complete, and no pending DTCs are stored, perform the following procedure.

13. Drive the vehicle at a speed between 75 and 100 km/h (47 and 63 mph) for 10 minutes or more [D].
    

    HINT:

    1. Drive the vehicle while keeping the engine load as constant as possible.
       
    2. The monitor item will change to Complete as the catalyst efficiency monitor operates [E].
       
14. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    
15. Check if any DTCs (pending DTCs) are stored.
    

    HINT:

    If Catalyst does not change to Complete, and no pending DTCs are stored, extend the driving time.

CONDITIONING FOR SENSOR TESTING

HINT:

Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the A/F and HO2 sensors. This is in order to activate the sensors sufficiently to obtain the appropriate inspection results.

1. (a) Connect the Techstream to the DLC3.
   
2. (b) Start the engine and warm it up with all the accessories switched off, until the engine coolant temperature stabilizes.
   
3. (c) Run the engine at an engine speed of between 2500 rpm and 3000 rpm for at least 3 minutes.
   
4. (d) While running the engine at 3000 rpm and 2000 rpm alternating at 2 second intervals, check the waveforms of the A/F and HO2 sensors using the Techstream.
   

HINT:

1. If either voltage output of the Air-Fuel Ratio (A/F) or Heated Oxygen (HO2) sensor does not fluctuate, or there is a noise in the waveform of either sensor the sensor may be malfunctioning.
   
2. If the voltage outputs of both the sensors remain lean or rich, the air-fuel ratio may be extremely lean or rich. In such cases, perform the following menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.
   
3. If the Three-Way Catalytic Converter (TWC) has deteriorated, the HO2 sensor (located behind the TWC) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).
   

INSPECTION PROCEDURE

HINT:

1. Sensor 1 refers to the sensor closest to the engine assembly.
   
2. Sensor 2 refers to the sensor farthest away from the engine assembly.
   
3. Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.
   

1. Connect a 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
   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.

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.
   

6. Perform the Active Test operation with the engine in an idling condition (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:

   1. Change the fuel injection volume within the range of -12% to +12%. The injection volume can be changed in fine gradations.
      
   2. Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
      
   3. 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.
      
   4. If the sensor output voltage does not change (almost no reaction) while performing the Active Test, the sensor may be malfunctioning.
      
   
   

   Standard Voltage:

   
   

   Techstream Display (Sensor)	Injection Volume	Status	Voltage
   AFS Voltage B1S1 (A/F)	+12%	Rich	Less than 3.1
   	-12%	Lean	More than 3.4
   O2S B1S2 (HO2)	+12%	Rich	More than 0.55
   	-12%	Lean	Less than 0.4

   
   

   Result

   Status AFS Voltage B1S1	Status O2S B1S2	A/F Condition and A/F and HO2 Sensor 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, the A/F sensor output voltage (AFS Voltage B1S1) is consistently more than 3.4 V, and the HO2 sensor output voltage (O2S B1S2) is consistently less than 0.4 V.
   Rich: During Control the Injection Volume, the AFS Voltage B1S1 is consistently less than 3.1 V, and the O2S B1S2 is consistently more than 0.55 V.
   Lean/Rich: During Control the Injection Volume of the Active Test, the output voltage of the HO2 sensor alternates correctly.
   

1. Check for exhaust gas leak.
   

OK:

No exhaust gas leak.

1. Replace the exhaust pipe assembly front (TWC: Front catalyst and rear catalyst) (YARIS_NCP93 RM000001J8701FX.html).
   

1. Replace the air fuel ratio sensor (bank 1 sensor 1) (YARIS_NCP93 RM000001CKA00YX.html).
   

1. Check for exhaust gas leak.
   

OK:

No exhaust gas leak.

1. Replace the heated oxygen sensor (bank 1 sensor 2) (YARIS_NCP93 RM000001CMD00WX.html).
   

1. Check for exhaust gas leak.
   

OK:

No exhaust gas leak.

1. Check the cause of extremely rich or lean actual air fuel ratio, referring to the DTC P0171 Inspection Procedure (YARIS_NCP93 RM000000WC30I9X_07.html).
   

1. Repair or replace exhaust gas leak point.
   

1. Connect the Techstream to the DLC3.
   

2. Turn the ignition switch to ON.
   

3. Turn the Techstream on.
   

4. Clear the DTCs (YARIS_NCP93 RM000000PDK0QGX.html).
   

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

6. Turn the ignition switch to ON.
   

7. Turn the Techstream on.
   

8. Start the engine.
   

9. Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
   

10. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
    

11. Read DTCs.
    

    Result

    Result	Proceed to
    DTC P0420 is output	A
    DTC is not output (No pending DTCs output)	B

1. Replace the exhaust pipe assembly front (TWC: Front catalyst and rear catalyst) (YARIS_NCP93 RM000001J8701FX.html).