P0420
2AR-FE ENGINE CONTROL: 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 sensor, sends pre-catalyst information to the ECM. The second sensor, the heated oxygen sensor, sends post-catalyst information to the ECM.
In order to detect any deterioration in the Three-way Catalytic Converter (TWC), the ECM calculates the Oxygen Storage Capacity (OSC) of the Three-way Catalytic Converter (TWC). This calculation is based on the voltage output of the heated oxygen sensor while performing active air-fuel ratio control.
The OSC value is an indication of the oxygen storage capacity of the Three-way Catalytic Converter (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 heated oxygen sensor is long, the OSC becomes greater. There is a direct correlation between the OSCs of the heated oxygen sensor and Three-way Catalytic Converter (TWC).
The ECM uses the OSC value to determine the state of the Three-way Catalytic Converter (TWC). If any deterioration has occurred, it illuminates the MIL and stores the DTC.
CATALYST LOCATION
Text in Illustration
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
HINT
The estimated catalyst temperature can be read in the Data List using the Techstream.
TYPICAL MALFUNCTION THRESHOLDS
MONITOR RESULT
Refer to detailed information in Checking Monitor Status Mode 6 Data.
P0420: Catalyst Efficiency / O2 STORAGE B1
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 the 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 / 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 (38 mph) for 10 minutes or more [B].
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 / 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 / Trouble Codes.
15. Check if any DTCs (pending DTCs) are stored.
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 and heated oxygen sensors. This is to activate the sensors sufficiently to obtain 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 then 2000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the Techstream.
HINT
- If the voltage output of either 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, perform the Control the Injection Volume for A/F Sensor Active Test using the Techstream.
- If the Three-way Catalytic Converter (TWC) has deteriorated, the heated oxygen sensor (located behind the Three-way Catalytic Converter (TWC)) voltage output fluctuates up and down frequently, even under normal driving conditions (active air-fuel ratio control is not performed).
Result of Real-vehicle Check
INSPECTION PROCEDURE
HINT
- After performing repairs, drive the vehicle in accordance with the driving pattern described in Confirmation Driving Pattern and check if DTC P0420 is output again. If a DTC is output again, replace the catalyst if it has not been replaced already.
- 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.
- Sensor 1 refers to the sensor closest to the engine assembly.
- Sensor 2 refers to the sensor farthest away from the engine assembly.
PROCEDURE
1. CHECK FOR 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 / 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 Engine Control - 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.
(c) Turn the Techstream on.
(d) Warm up the engine and run the engine at an engine speed of 2500 rpm for approximately 90 seconds.
(e) Enter the following menus: Powertrain / Engine / Active Test / Control the Injection Volume.
(f) Perform the Control the Injection Volume operation with the engine idling.
(g) Monitor the voltage outputs of the air fuel ratio and heated oxygen sensors (AFS Voltage B1S1 and O2S B1S2) displayed on the Techstream.
HINT
- Change the fuel injection volume within the range of - 12.0% to +12.0%. The injection volume can be changed in fine gradations.
- 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.
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 air fuel ratio sensor and heated oxygen sensor alternate correctly.
(h) Refer to "Data List / Active Test" [AFS Voltage B1S1 and O2S B1S2] Data List / Active List.
D -- CHECK FOR EXHAUST GAS LEAK
C -- CHECK FOR EXHAUST GAS LEAK
B -- REPLACE AIR FUEL RATIO SENSOR Removal
A -- Continue to next step.
3. CHECK FOR EXHAUST GAS LEAK
(a) Inspect for exhaust gas leaks from the exhaust manifold sub-assembly and exhaust pipes.
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 Removal.
NEXT -- REPLACE CENTER EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST) Removal
5. CHECK FOR EXHAUST GAS LEAK
(a) Inspect for exhaust gas leaks from the exhaust manifold assembly and exhaust pipes.
OK:
No gas leaks.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- REPLACE HEATED OXYGEN SENSOR Removal
6. CHECK FOR EXHAUST GAS LEAK
(a) Inspect for exhaust gas leaks from the exhaust manifold assembly and exhaust pipes.
OK:
No gas leaks.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- CHECK CAUSE OF EXTREMELY RICH OR LEAN ACTUAL AIR FUEL RATIO