P0420

2AZ-FXE ENGINE CONTROL: SFI SYSTEM: P0420: Catalyst System Efficiency Below Threshold (Bank 1)
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

MONITOR DESCRIPTION

The hybrid vehicle control ECU uses sensors mounted in front of and behind the three-way catalytic converter to monitor its efficiency.

The first sensor, the air fuel ratio sensor, sends pre-catalyst information to the hybrid vehicle control ECU. The second sensor, the heated oxygen sensor, sends post-catalyst information to the hybrid vehicle control ECU.

In order to detect any deterioration in the three-way catalytic converter, the hybrid vehicle control ECU calculates the oxygen storage capacity of the three-way catalytic converter. This calculation is based on the voltage output of the heated oxygen sensor while performing active air fuel ratio control.

The oxygen storage capacity value is an indication of the oxygen storage capacity of the three-way catalytic converter. When the vehicle is being driven with a warm engine, active air fuel ratio control is performed for approximately 15 to 25 seconds. When it is performed, the hybrid vehicle control ECU deliberately sets the air fuel ratio to lean or rich levels. If the cycle of the waveform for the heated oxygen sensor is long, the oxygen storage capacity is great. There is a direct correlation between the heated oxygen sensor and the oxygen storage capacity of the three-way catalytic converter.

The hybrid vehicle control ECU uses the oxygen storage capacity value to determine the state of the three-way catalytic converter. If any deterioration has occurred, it illuminates the MIL and stores the DTC.

This system determines the deterioration of the entire catalyst system (including the front and rear catalysts), by using the oxygen storage capacity value of the front catalyst, that is more sensitive than the rear catalyst, as the representative value. Therefore, be sure to replace the front and rear catalysts together when catalyst replacement is necessary.





HINT
- Bank 1 sensor 1 refers to the sensor closest to the engine assembly.
- Bank 1 sensor 2 refers to the sensor farthest away from the engine assembly.

CATALYST LOCATION





Text in Illustration





NOTICE:
Replace the exhaust manifold converter sub-assembly (*1) and the center exhaust pipe assembly (*5) together when catalyst replacement is necessary. (Excluding air fuel ratio sensor*2)

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





MONITOR RESULT

Refer to Checking Monitor Status Mode 6 Data.

CONFIRMATION DRIVING PATTERN

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





1. Connect the Techstream to the DLC3.

2. Turn the power switch on (IG).

3. Turn the Techstream on.

4. Clear the DTCs (even if no DTCs are stored, perform the clear DTC procedure) Reading and Clearing Diagnostic Trouble Codes.

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

6. Turn the power switch on (IG) 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. Put the engine in inspection mode (maintenance mode) Component Tests and General Diagnostics.

10. Start the engine and warm it up (until the engine coolant temperature is 75°C (167°F) or higher) [A].

11. Drive the vehicle at approximately 60 km/h (38 mph) for 10 minutes or more [B].

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

HINT
- Drive the vehicle while keeping the engine load as constant as possible.
- The monitor item will change to Complete as the Catalyst Efficiency monitor operates [C].

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

13. 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.

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

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

HINT
- Drive the vehicle while keeping the engine load as constant as possible.
- The monitor item will change to Complete as the Catalyst Efficiency monitor operates [E].

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

16. Check if any DTCs (pending DTCs) are set.

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

17. If no pending DTC is output, perform a universal trip and check for permanent DTCs Reading and Clearing Diagnostic Trouble Codes.

HINT
- If a permanent DTC is output, the system is malfunctioning.
- If no permanent DTC is output, the system is normal.

CONDITIONING FOR SENSOR TESTING

HINT
Perform the operation with the engine speeds and time durations described below prior to checking the waveforms of the air fuel ratio sensor and heated oxygen sensor. This is to activate the sensors sufficiently to obtain the appropriate inspection results.





- (a) Connect the Techstream to the DLC3 [A].
- (b) Turn the power switch on (IG) and turn the Techstream on [B].
- (c) Put the engine in inspection mode (maintenance mode) Component Tests and General Diagnostics [C].
- (d) Start the engine and warm it up with all the accessories switched off until the engine coolant temperature stabilizes [D].
- (e) Run the engine at an engine speed of 2500 rpm for at least 3 minutes [E].
HINT
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, perform step [E] after charging control has completed.

- (f) While running the engine at 2500 rpm for 2 seconds and 1500 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the Techstream [F].

HINT
- If either voltage output of the air fuel ratio or heated oxygen sensor does not fluctuate, or there is noise in the waveform of either sensor, the sensor may be malfunctioning.
- 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, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.
- If the three-way catalytic converter has deteriorated, the heated oxygen sensor (located behind the three-way catalytic converter) voltage output fluctuates up and down frequently, even under normal driving conditions (active air fuel ratio control is not performed).






INSPECTION PROCEDURE

HINT
Read freeze frame data using the Techstream. The hybrid vehicle control ECU 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.

PROCEDURE

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

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(e) Read the DTCs.

Result:





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

B -- GO TO DTC CHART SFI System
A -- Continue to next step.

2. PERFORM ACTIVE TEST USING TECHSTREAM (CONTROL THE INJECTION VOLUME)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Put the engine in inspection mode (maintenance mode) Component Tests and General Diagnostics.

(e) Start the engine warm it up.

(f) Run up the engine at an engine speed of 2500 rpm for approximately 90 seconds.

HINT
During charging control, the engine speed is set at idle. Therefore, the engine speed does not increase when depressing the accelerator pedal. In this case, warm up the engine after charging control has completed.

(g) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume / Data List / AFS Voltage B1S1 and O2S B1S2.

(h) Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).

(i) Monitor the output voltages of the air fuel ratio sensor and heated oxygen sensor (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.

HINT
- Change the fuel injection volume within the range of -12% to +12%. The injection volume can be changed in fine gradations.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
- 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.





Result





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 heated oxygen sensor alternates correctly.

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

C -- CHECK FOR EXHAUST GAS LEAK

D -- CHECK FOR EXHAUST GAS LEAK
A -- Continue to next step.

3. CHECK FOR EXHAUST GAS LEAK

(a) Check for exhaust gas leaks.

OK:

No gas leaks.

NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- Continue to next step.

4. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY (TWC: FRONT CATALYST) AND CENTER EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST)

NOTICE:
Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst) and the center exhaust pipe assembly (TWC: Rear catalyst) together when catalyst replacement is necessary.

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

(a) Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst) Components.

(b) Replace the center exhaust pipe assembly (TWC: Rear catalyst) Components.

NEXT -- END

5. REPLACE AIR FUEL RATIO SENSOR (SENSOR 1)

(a) Replace the air fuel ratio sensor Removal.

NEXT -- CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)

6. CHECK FOR EXHAUST GAS LEAK

(a) Check for exhaust gas leaks.

OK:

No gas leaks.

NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- Continue to next step.

7. REPLACE HEATED OXYGEN SENSOR (SENSOR 2)

(a) Replace the heated oxygen sensor Removal.

NEXT -- CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)

8. CHECK FOR EXHAUST GAS LEAK

(a) Check for exhaust gas leaks.

OK:

No gas leaks.

NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- Continue to next step.

9. CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO

(a) Check the case of extremely rich or lean actual air fuel ratio, referring to the DTC P0171 Inspection Procedure P0171.

NEXT -- CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)

10. REPAIR OR REPLACE EXHAUST GAS LEAK POINT

(a) Repair or replace exhaust gas leak point.

NEXT -- Continue to next step.

11. CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Turn the Techstream on.

(d) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.

(e) Turn the power switch off and wait for at least 30 seconds.

(f) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.

(g) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.

(h) Read the DTCs.

Result





B -- END
A -- Continue to next step.

12. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY (TWC: FRONT CATALYST) AND CENTER EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST)

NOTICE:
Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst) and the center exhaust pipe assembly (TWC: Rear catalyst) together when catalyst replacement is necessary.

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

(a) Replace the exhaust manifold converter sub-assembly (TWC: Front catalyst) Components.

(b) Replace the center exhaust pipe assembly (TWC: Rear catalyst) Components.

NEXT -- END