CONDITIONING FOR SENSOR TESTING
CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 AND/OR P0430)
PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR)
CHECK DTC OUTPUT (DTC P0420 AND/OR P0430)
REPLACE EXHAUST MANIFOLD (BANK 1) (TWC: FRONT CATALYST)
REPLACE EXHAUST MANIFOLD (BANK 2) (TWC: FRONT CATALYST)
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 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.
| DTC Code | DTC Detection Condition | Trouble Area |
| P0420 | The OSC value is smaller than the standard value under active air fuel ratio control (2 trip detection logic). |
|
| P0430 | The OSC value is smaller than the standard value under active air fuel ratio control (2 trip detection logic). |
|
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.
Catalyst location
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 intelligent tester 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 alternately 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 intelligent tester.
HINT:
- If either voltage output of the Air Fuel Ratio (A/F) or Heated Oxygen (HO2) 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, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
- 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:
Malfunctioning areas can be identified by performing the Control the Injection Volume for A/F sensor function provided in the Active Test. The Control the Injection Volume for A/F sensor function can help to determine whether the Air Fuel Ratio (A/F) sensor, Heated Oxygen (HO2) sensor and other potential trouble areas are malfunctioning.
The following instructions describe how to conduct the Control the Injection Volume for A/F sensor operation using the intelligent tester.
- Connect the intelligent tester to the DLC3.
- Start the engine and turn the intelligent tester on.
- Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
- On the intelligent tester, enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
- Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume.)
- Monitor the output voltages of the A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2, or AFS Voltage B2S1 and O2S B2S2) displayed on the intelligent 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.
| Tester Display (Sensor) | Injection Volume | Status | Voltage |
| AFS Voltage B1S1 or AFS Voltage B2S1 (A/F) | +25% | Rich | Less than 3.1 V |
| AFS Voltage B1S1 or AFS Voltage B2S1 (A/F) | -12.5% | Lean | More than 3.4 V |
| O2S B1S2 or O2S B2S2 (HO2) | +25% | Rich | More than 0.55 V |
| O2S B1S2 or O2S B2S2 (HO2) | -12.5% | Lean | Less than 0.4 V |
NOTICE:
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.
| Case | A/F Sensor (Sensor 1) Output Voltage | HO2 Sensor (Sensor 2) Output Voltage | Main Suspected Trouble Area |
| 1 |   |
 |
- |
| 2 |  |
|
|
| 3 | |
|
|
| 4 | |
|
|
- 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 Voltage B1S1 and O2S B1S2 or AFS Voltage B2S1 and O2S B2S2.
HINT:
Read freeze frame data using the intelligent tester. 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.
| 1.CHECK ANY OTHER DTCS OUTPUT (IN ADDITION TO DTC P0420 AND/OR P0430) |
-
Connect the intelligent tester to the DLC3.
-
Turn the ignition switch to ON and turn the intelligent tester on.
-
Enter the following menus: Powertrain / Engine and ECT / Trouble Codes.
-
Read DTCs.
Result Display (DTC Output) Proceed to P0420 and/or P0430 A P0420 and/or P0430 and other DTCs B HINT:
If any DTCs other than P0420 or P0430 are output, troubleshoot those DTCs first.
|
|
||||
| A | |
| 2.PERFORM ACTIVE TEST USING INTELLIGENT TESTER (CONTROL THE INJECTION VOLUME FOR A/F SENSOR) |
-
Connect the intelligent tester to the DLC3.
-
Start the engine and turn the intelligent tester on.
-
Warm up the engine at an engine speed of 2500 rpm for approximately 90 seconds.
-
Enter the following menus: Powertrain / Engine and ECT / Active Test / Control the Injection Volume for A/F sensor.
-
Perform the Active Test operation with the engine idling (press the RIGHT or LEFT button to change the fuel injection volume).
-
Monitor the voltage outputs of the A/F and HO2 sensors (AFS Voltage B1S1 and O2S B1S2 or AFS, Voltage B2S1 and O2S B2S2) displayed on the intelligent 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.
Standard:
Tester Display (Sensor) Injection Volume Status Voltage AFS Voltage B1S1 or AFS Voltage B2S1 (A/F) +25% Rich Less than 3.1 AFS Voltage B1S1 or AFS Voltage B2S1 (A/F) -12.5% Lean More than 3.4 O2S B1S2 or O2S B2S2 (HO2) +25% Rich More than 0.55 O2S B1S2 or O2S B2S2 (HO2) -12.5% Lean Less than 0.4 Result:
Status AFS Voltage B1S1 or AFS Voltage B2S1 Status O2S B1S2 or O2S B2S2 A/F Condition and A/F and HO2 Sensors Condition Misfire Main Suspected Trouble Area Proceed to Lean/Rich Lean/Rich Normal - - Three-Way Catalytic Converter (TWC)
- Gas leakage from exhaust system
A Lean Lean/Rich A/F sensor malfunction - - A/F sensor
B Rich Lean/Rich A/F sensor malfunction - - A/F sensor
Lean/Rich Lean HO2 sensor malfunction - - HO2 sensor
- Gas leakage from exhaust system
C Lean/Rich Rich HO2 sensor malfunction - - HO2 sensor
- Gas leakage from exhaust system
Lean Lean Actual air fuel ratio lean May occur - Extremely rich or lean actual air fuel ratio
- Gas leakage from exhaust system
A Rich Rich Actual air fuel ratio rich - - Extremely rich or lean actual air fuel ratio
- Gas leakage from exhaust system
Lean: During Control the Injection Volume for A/F sensor, the A/F sensor output voltage (AFS) is consistently more than 3.4 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 3.1 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.
|
|
||||
|
|
||||
|
|
||||
| A | |
| 3.INSPECT FOR EXHAUST GAS LEAK |
-
Inspect for exhaust gas leakage from the exhaust manifold sub-assembly and exhaust pipe.
OK:
No gas leakage.
Result Result Proceed to NG A OK B
|
|
||||
| A | |
|
| 4.INSPECT EXHAUST GAS LEAK |
-
Inspect for exhaust gas leakage from the exhaust manifold sub-assembly and exhaust pipe.
OK:
No gas leakage.
|
|
||||
| OK | |
|
| 5.CHECK DTC OUTPUT (DTC P0420 AND/OR P0430) |
-
According to the output DTCs in the step "Check Any Other DTCs Output", proceed to the next step by referring to the table below.
Result Result Proceed to P0420 A P0430 B P0420 and P0430 A and B
|
|
||||
| A | |
| 6.REPLACE EXHAUST MANIFOLD (BANK 1) (TWC: FRONT CATALYST) |
-
Replace the exhaust manifold .
| NEXT | |
|
| 7.REPLACE EXHAUST MANIFOLD (BANK 2) (TWC: FRONT CATALYST) |
-
Replace the exhaust manifold .
| NEXT | |
|