P0420
2ZR-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P0420: Catalyst System Efficiency Below Threshold (Bank 1)
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
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 a 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 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.
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 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 (37 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].
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
- 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].
14. Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
15. Check if any DTCs (pending DTCs) are stored.
HINT
If monitor item does not change to Complete, and no pending DTCs are stored, extend the driving time.
16. 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 (A/F) sensor and Heated Oxygen (HO2) sensor. 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 for 2 seconds and 2000 rpm for 2 seconds, check the waveforms of the A/F and HO2 sensors using the Techstream.
HINT
- If either of the voltage outputs of the A/F or HO2 sensor does not fluctuate, or either of the sensors makes a noise, 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 menu items: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.
- 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
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
- 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.
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(e) Read 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) Start the engine and warm it up.
(c) Turn the Techstream on.
(d) Run the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(e) Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume.
(f) Perform the Active Test 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 air fuel ratio sensor and heated oxygen sensor (AFS B1S1AFS 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.
Standard:
Result
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.
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 leak.
OK:
No gas leak.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- Continue to next step.
4. REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST)
HINT
Confirm the replacement parts, referring to the illustration in the Catalyst Location.
(a) Replace the front exhaust pipe assembly (TWC: Front catalyst and rear catalyst) Removal.
NEXT -- END
5. REPLACE AIR FUEL RATIO SENSOR (SENSOR 1)
(a) Replace the air fuel ratio sensor (sensor 1) Removal.
NEXT -- CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)
6. CHECK FOR EXHAUST GAS LEAK
(a) Check for exhaust gas leak.
OK:
No gas leak.
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 (sensor 2) Removal.
NEXT -- CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)
8. CHECK FOR EXHAUST GAS LEAK
(a) Check for exhaust gas leak.
OK:
No gas leak.
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 cause 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 Components.
NEXT -- Continue to next step.
11. CHECK WHETHER DTC OUTPUT RECURS (DTC P0420)
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch to ON.
(c) Turn the Techstream on.
(d) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.
(e) Turn the ignition switch to ON.
(f) Turn the Techstream on.
(g) Start the engine.
(h) Drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern.
(i) Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
(j) Read the pending DTCs.
Result
B -- END
A -- Continue to next step.
12. REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: FRONT CATALYST AND REAR CATALYST)
HINT
Confirm the replacement parts, referring to the illustration in the Catalyst Location.
(a) Replace the front exhaust pipe assembly (TWC: Front catalyst and rear catalyst) Components.
NEXT -- END