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P0420








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

DTC P0420 - Catalyst System Efficiency Below Threshold (Bank 1)

MONITOR DESCRIPTION

The ECM (included in 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 (A/F) sensor, sends pre-catalyst information to the ECM. The second sensor, the Heated Oxygen (HO2) sensor, sends post-catalyst information to the ECM.
In order to detect any deterioration in the TWC, the ECM calculates the Oxygen Storage Capacity (OSC) of the TWC. This calculation is based on the voltage output of the HO2 sensor while performing active air- fuel ratio control, rather than the conventional detecting method, which uses the locus ratio.
The OSC value is an indication of the oxygen storage capacity of the TWC. When the vehicle is being driven with a warm engine, active air-fuel ratio control is performed for approximately 15 to 20 seconds. When it is performed, the ECM deliberately sets the air-fuel ratio to lean or rich levels. If the cycle of the waveform for the HO2 sensor is long, the OSC great. There is a direct correlation between the HO2 sensor and the OSC of the TWC.
The ECM uses the OSC value to determine the state of the TWC. If any deterioration has occurred, it illuminates the MIL and sets the DTC.






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 pattern will activate the catalyst monitor. This is very useful for verifying completion of a repair.




(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Turn the tester on.
(d) Clear the DTCs (if set) DTC Check / Clear.
(e) Select the following menu items: Powertrain / Engine / Monitor.
(f) Check that Catalyst / Status 2 is Incomplete.
(g) Put the engine in inspection mode Component Tests and General Diagnostics, and warm it up.
(h) Drive the vehicle at between 40 mph and 70 mph (64 km/h and 113 km/h) for at least 10 minutes.
(i) Note the state of the Readiness Tests items. Those items will change to Complete as catalyst / Status monitor operates.
(j) On the tester, select the following menu items: Powertrain / Engine / Trouble Code / Pending and check if any DTCs (any pending DTCs) are set.
HINT: If Catalyst / Status 2 does not change to Complete, and any pending DTCs fail to be set, 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.




(a) Connect the Techstream to the DLC3.
(b) Put the engine in inspection mode Component Tests and General Diagnostics, and warm it up with all the accessories switched OFF, until the engine coolant temperature stabilizes.
(c) Run the engine at an engine speed of between 2,500 rpm and 3,000 rpm for at least 3 minutes.
(d) While running the engine at 3,000 rpm and 2,000 rpm alternating at 2 second intervals, check the waveforms of the A/F and HO2 sensors using the tester.
HINT:
- 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.
- 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 A/F CONTROL using the Techstream.
- 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: Read freeze frame data using the Techstream. The ECM (included in 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) and turn the tester on.
(c) Select the following menu items: Powertrain / Engine / Trouble Code.
(d) Read the DTCs.
Result:





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

B -- GO TO DTC CHART
A -- Continue to next step.
2. PERFORM ACTIVE TEST USING TECHSTREAM (A/F CONTROL)
(a) Connect the Techstream to the DLC3.
(b) Put the engine in inspection mode Component Tests and General Diagnostics.
(c) Turn the tester on.
(d) Warm up the engine at an engine speed of 2,500 rpm for approximately 90 seconds.
(e) On the tester, select the following menu items: Powertrain / Engine / Active Test / Control the Injection Volume for A/F sensor.
(f) Perform the Control the Injection Volume for A/F sensor operation with the engine in an idling condition (press the RIGHT or LEFT button to change the fuel injection volume).
(g) Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2) displayed on the tester.
Result:
A/F sensor reacts in accordance with increases and decreases in fuel injection volume:
+25% = Rich output
Less than 3.0 V
-12.5% = Lean output
More than 3.35 V
NOTICE: The A/F sensor has an output delay of a few seconds and the HO2 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 A/F and HO2 sensors.
- To display the graph, select the following menu items on the tester: Powertrain / Engine / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 and O2S B1 S2 then press the graph button on the Data List view.

Result:






D -- CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR-FUEL RATIO, REPLACE FAULTY AREA AND GO TO NEXT STEP
C -- INSPECT FOR EXHAUST GAS LEAK
B -- REPLACE AIR FUEL RATIO SENSOR
A -- Continue to next step.
3. INSPECT FOR EXHAUST GAS LEAK
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT
OK -- Continue to next step.
4. REPLACE EXHAUST MANIFOLD CONVERTER SUB-ASSEMBLY
(a) Replace exhaust manifold converter sub-assembly Removal.
NEXT -- REPLACE FRONT EXHAUST PIPE ASSEMBLY
5. INSPECT FOR EXHAUST GAS LEAK
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT
OK -- REPLACE HEATED OXYGEN SENSOR
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