P0420

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

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

DTC P0430 - Catalyst System Efficiency Below Threshold (Bank 2)

MONITOR DESCRIPTION

The ECM 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.
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 rich-lean cycle of the HO2 sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the HO2 sensor and 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.





HINT:
- Bank 1 refers to the bank that includes No. 1 cylinder.
- Bank 2 refers to the bank that does not include No. 1 cylinder.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.

MONITOR STRATEGY





TYPICAL ENABLING CONDITIONS





TYPICAL MALFUNCTION THRESHOLDS





For Mexico Models:





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 the completion of a repair.





- (a) Connect the Techstream to the DLC3.

- (b) Turn the ignition switch to ON.

- (c) Turn the Techstream ON.

- (d) Clear DTCs (if set) (DTC Check / Clear).

- (e) Enter the following menus: Powertrain / Engine and ECT / Data List / All / Catalyst Monitor CMPL.

- (f) Check that Catalyst Monitor CMPL is incomplete.

- (g) Start the engine and warm it up.

- (h) Drive the vehicle at between 64 km/h and 113 km/h (40 mph and 70 mph) for at least 10 minutes.

- (i) Note the state of the Readiness Tests items. Those items will change to Complete as Catalyst Monitor CMPL monitor operates.

- (j) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes / Pending.

- (k) Check if any DTCs (any pending DTCs) are set.

HINT: If Catalyst Monitor CMPL does not change to Complete, and any pending DTCs fail to 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) Start the engine 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 2500 rpm and 3000 rpm for at least 3 minutes.

- (d) While running the engine at 3000 rpm and 2000 rpm at 2 second intervals, check the waveforms of the A/F and HO2 sensors using the Techstream.

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 Control the Injection Volume for A/F Sensor 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. Freeze frame data records the engine condition when malfunctions are detected. 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 OR P0430)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON and turn the Techstream ON.
(c) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(d) Read DTCs.

Result





HINT: If any DTCs other than P0420 or P0430 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) Start the engine and turn the Techstream ON.
(c) Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(d) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor.
(e) 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).
(f) Monitor the voltage outputs of the A/F and HO2 sensors (AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2) displayed on the Techstream.
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

NOTE: 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, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/ F Sensor / A/F Control System / AFS B1 S1 and O2S B1 S2 or AFS B2 S1 and O2S B2 S2.

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.

Result





B -- CHECK DTC OUTPUT (DTC P0420 AND / OR P0430)
A -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
4. INSPECT FOR EXHAUST GAS LEAK
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- REPLACE HEATED OXYGEN SENSOR
5. CHECK DTC OUTPUT (DTC P0420 AND / OR P0430)
(a) According to the output DTCs in the step 1 (Check Any Other DTCs Output), proceed to next step referring to the table below.
Result:





D -- REPLACE FRONT NO. 2 EXHAUST PIPE ASSEMBLY
C -- REPLACE FRONT NO. 2 EXHAUST PIPE ASSEMBLY (FRONT NO. 2 AND NO. 3 EXHAUST PIPE SUB-ASSEMBLY)
B -- REPLACE FRONT EXHAUST PIPE ASSEMBLY
A -- REPLACE FRONT EXHAUST PIPE ASSEMBLY