P0420
4GR-FSE 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, 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 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 sets a DTC.
HINT:
- Bank 1 refers to the bank that includes cylinder No. 1.
- Bank 2 refers to the bank that does not include cylinder No. 1.
- 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
MONITOR RESULT
Refer to CHECKING MONITOR STATUS Mode 6 Data.
CONDITIONING FOR SENSOR TESTING
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 performed in order to heat the sensors sufficiently to obtain the appropriate inspection results.
1. Connect Techstream to the DLC3 (Procedure "A").
2. Start the engine and warm it up with all the accessories switched OFF, until the engine coolant temperature stabilizes (Procedure "B").
3. Run the engine at engine speed of between 2,500 rpm and 3,000 rpm for at least 3 minutes (Procedure "C").
4. While running the engine at 3,000 rpm for 2 seconds and 2,000 rpm for 2 seconds, check the waveforms of the A/F and HO2 sensors using the tester or scan tool (Procedure "D").
NOTE: The Air Fuel Ratio (A/F) sensor has an output delay of a few seconds and the Heated Oxygen (HO2) sensor has a maximum output delay of approximately 20 seconds.
- Following the A/F CONTROL procedure enables technicians to check and graph the output voltages of both the A/F and HO2 sensors.
- To display the graph, enter the following menus on the tester: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F Sensor / A/F Control System / AFS B1 S1 or AFS B2 S1 and O2S B1 S2 or O2S B2 S2. Then press the graph button on the Data List view.
INSPECTION PROCEDURE
HINT: Read freeze frame data using 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 be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air/fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction Freeze Frame Data.
PROCEDURE
1. CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 AND/OR P0430)
(a) Connect Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the tester 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 Techstream to the DLC3.
(b) Start the engine and turn the tester on.
(c) Warm up the engine at engine speed of 2,500 rpm for approximately 90 seconds.
(d) On the tester, 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 output voltages 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 tester.
HINT:
- The Control the Injection Volume for A/F Sensor operation lowers the fuel injection volume by 12.5 % or increases the injection volume by 25 %.
- Each sensor reacts in accordance with increases and decreases in the fuel injection volume.
Result:
- Lean:
During Control the Injection Volume for A/F Sensor, the A/F sensor (AFS) output voltage is consistently more than 3.35 V, and the HO2 sensor output voltage (O2S) is consistently less than 0.4 V.
- Rich:
During Control the Injection Volume for A/F Sensor, the AFS is consistently less than 3.0 V, and the O2S is consistently more than 0.55 V.
- Lean/Rich:
During Control the Injection Volume for A/F Sensor of the Active Test, the output voltage of the HO2 sensor alternates correctly.
C -- CHECK AND REPLACE HEATED OXYGEN SENSOR, AND CHECK AND REPAIR EXHAUST GAS LEAKAGE
B -- CHECK AND REPLACE AIR FUEL RATIO SENSOR
A -- Continue to next step.
3. CHECK FOR EXHAUST GAS LEAK
OK:
No gas leakage.
NG -- REPAIR OR REPLACE EXHAUST GAS LEAKAGE POINT
OK -- Continue to next step.
4. CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)
(a) Connect Techstream to the DLC3.
(b) Turn the engine switch on (IG) and turn the tester on.
(c) Select the following menu items: Powertrain / Engine and ECT / Trouble Codes.
(d) Read the DTCs.
Result:
B -- REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY LH
A -- Continue to next step.
5. REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY RH
(a) Replace the exhaust manifold sub-assembly RH Removal.
NEXT -- REPLACE FRONT EXHAUST PIPE ASSEMBLY
6. REPLACE EXHAUST MANIFOLD SUB-ASSEMBLY LH
(a) Replace the exhaust manifold sub-assembly LH Removal.
NEXT -- REPLACE FRONT EXHAUST PIPE ASSEMBLY