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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 (TWC) 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, the hybrid vehicle control ECU illuminates the MIL and sets the DTC.





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





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 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.

8. Check that Catalyst Efficiency / Status2 is Incomplete.

9. Put the engine in inspection 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 / 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 / Trouble Codes / Pending.

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

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 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 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].
- (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 / Active Test / Control the Injection Volume for A/F Sensor.
- 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

1. AIR FUEL RATIO CONTROL

HINT
Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F Sensor function provided in the Active Test. The Control the Injection Volume for A/F Sensor function can help to determine whether the air fuel ratio sensor, heated oxygen sensor and other potential trouble areas are malfunctioning.

The following instructions describe how to conduct the Control the Injection Volume for A/F Sensor operation using the Techstream.

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG) and turn the Techstream on.

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

(d) Start the engine.

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

(f) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.

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

(h) Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (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.





NOTICE:
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.





Following the Control the Injection Volume for A/F Sensor procedure enables technicians to check and graph the voltage outputs of both the air fuel ratio and heated oxygen sensors.

To display the graph, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS Voltage B1S1 and O2S B1S2.

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 FOR A/F SENSOR)

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG) and turn the Techstream on.

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

(d) Start the engine and warm it up.

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

(f) Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor.

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

(h) 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:





Result:





Lean: During Control the Injection Volume for A/F Sensor, the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 3.4 V, and the heated oxygen sensor output voltage (O2S B1S2) is consistently below 0.4 V.
Rich: During Control the Injection Volume for A/F Sensor, the AFS Voltage B1S1 is consistently below 3.1 V, and the O2S B1S2 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 heated oxygen sensor alternates correctly.

D -- GO TO NEXT STEP AFTER CHECKING ENGINE TO DETERMINE CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO P0171

C -- INSPECT FOR EXHAUST GAS LEAK

B -- REPLACE AIR FUEL RATIO SENSOR Removal
A -- Continue to next step.

3. INSPECT FOR EXHAUST GAS LEAK

(a) Inspect 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)

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

NEXT -- REPLACE CENTER EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST) Components

5. INSPECT FOR EXHAUST GAS LEAK

(a) Inspect for exhaust gas leaks.

OK:

No gas leaks.

NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT

OK -- REPLACE HEATED OXYGEN SENSOR Removal
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