P0420
FA20 ENGINE CONTROL: SFI SYSTEM: P0420; Catalyst System Efficiency Below Threshold (Bank 1); 2013 MY FR-S [03/2012 -]
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
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, the ECM calculates the oxygen storage capacity of the three-way catalytic converter. This calculation is based on the voltage output of the heated oxygen sensor.
The ECM uses the oxygen storage capacity value to determine the state of the three-way catalytic converter. If any deterioration has occurred, the ECM 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
MONITOR DESCRIPTION
The ECM uses diagnostic values to determine deterioration of the catalyst. If the diagnostic value exceeds a specified value, the catalyst is considered deteriorated, and the DTC is stored.
The diagnostic values are based upon the catalyst monitor value (CM) calculated by changes in the air fuel ratio sensor lambda and changes in the heated oxygen sensor output voltage, and in the response rate calculated from the heated oxygen sensor response time.
*: Diagnostic Value = CM X (1 + Response rate)
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
*: Refer to Monitor Description
MONITOR RESULT
Refer to Checking Monitor Status Mode 6 Data.
CONFIRMATION DRIVING PATTERN
1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON and turn the Techstream on.
3. Clear DTCs (even if no DTCs are stored, perform the clear DTC operation) Reading and Clearing Diagnostic Trouble Codes.
4. Turn the ignition switch off and wait for at least 30 seconds.
5. Turn the ignition switch to ON and turn the Techstream on.
6. Start the engine and warm it up until the engine coolant temperature reaches 75°C (167°F) or higher.
HINT
Check the engine coolant temperature is 20°C (68°F) or less at engine started.
7. Perform the following the confirmation driving pattern.
CAUTION:
When performing the confirmation driving pattern, obey all speed limits and traffic laws.
a. Drive the vehicle at 80 km/h (50 mph) or more for 20 minutes or more [A].
b. Stop the vehicle.
c. Idle the engine for 1 minute or more [B].
8. Enter the following menus: Powertrain / Engine / Trouble Codes.
9. Read pending DTCs.
HINT
* If a pending DTC is output, the system is malfunctioning.
* If a pending DTC is not output, perform the following procedure.
10. Enter the following menus: Powertrain / Engine / Utility / All Readiness.
11. Input the DTC: P0420.
12. Check the DTC judgment result.
HINT
* If the judgment result shows NORMAL, the system is normal.
* If the judgment result shows ABNORMAL, the system has a malfunction.
13. If the test result is INCOMPLETE or N/A and no 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
1. Connect the Techstream to the DLC3 [A].
2. Start the engine and warm it up with all the accessories switched off, until the engine coolant temperature stabilizes [B].
3. Run the engine at an engine speed of between 2500 rpm and 3000 rpm for at least 3 minutes [C].
4. While running the engine at 3000 rpm and 2000 rpm for 2 seconds, check the waveforms of the air fuel ratio and heated oxygen sensors using the Techstream [D].
HINT
* If either of the voltage outputs of either the air fuel ratio or heated oxygen 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, 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.
INSPECTION PROCEDURE
HINT
* If a malfunction cannot be found when troubleshooting DTC P0420, a lean or rich abnormality may be the cause. Perform troubleshooting by following the inspection procedure for P0171 (System Too Lean) and P0172 (System Too Rich).
* Bank 1 refers to the bank that includes the No. 1 cylinder*.
*: The No. 1 cylinder is the cylinder which is farthest from transmission.
* Bank 2 refers to the bank that does not include the 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.
* 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
(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 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 / Active Test / Control the Injection Volume
(f) Perform the Active Test operation with the engine idling (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 Voltage B1S1 and O2S B1S2) displayed on the Techstream.
HINT
* Change the fuel injection volume within the range of - 12% to +12%.
* 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 for A/F Sensor, the air fuel ratio sensor output voltage (AFS Voltage B1S1) is consistently higher than 2.4 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 2.0 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 air fuel ratio sensor and heated oxygen sensor alternate correctly.
B -- REPLACE AIR FUEL RATIO SENSOR Removal
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 leaks.
OK:
No gas leaks.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- Continue to next step.
4. REPLACE EXHAUST MANIFOLD (TWC: FRONT CATALYST)
(a) Replace the exhaust manifold (TWC: front catalyst) Removal.
NEXT -- REPLACE FRONT EXHAUST PIPE ASSEMBLY (TWC: REAR CATALYST) Removal
5. CHECK FOR EXHAUST GAS LEAK
(a) Check for exhaust gas leaks.
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) Check for exhaust gas leaks.
OK:
No gas leaks.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAK POINT
OK -- CHECK CAUSE OF EXTREMELY RICH OR LEARN ACTUAL AIR FUEL RATIO P0171