Toyota 2GR-FE Manual page 413

DTC P0420
DTC P0430
MONITOR DESCRIPTION
The ECM uses the 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.
DTC No.
OSC value is smaller than standard value under active
P0420
air-fuel ratio control (2 trip detection logic)
OSC value is smaller than standard value under active
P0430
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.
MONITOR STRATEGY
Related DTCs
Required Sensors/Components (Main)
Required Sensors/Components (Sub)
Frequency of Operation
Duration
MIL Operation
Sequence of Operation
2GR-FE ENGINE CONTROL SYSTEM – SFI SYSTEM
Catalyst System Efficiency Below Threshold
(Bank 1)
Catalyst System Efficiency Below Threshold
(Bank 2)
DTC Detection Condition
P0420: Catalyst Deterioration
P0420: Catalyst Deterioration
TWC
A/F sensor, heated oxygen sensor, intake air temperature sensor, mass air flow
meter, crankshaft position sensor and engine coolant temperature sensor
Once per driving cycle
Approximately 30 seconds
2 driving cycles
None
Trouble Area
• Gas leakage from exhaust system
• A/F sensor (bank 1 sensor 1)
• HO2 sensor (bank 1 sensor 2)
• Exhaust manifold (TWC)
• Gas leakage from exhaust system
• A/F sensor (bank 2 sensor 1)
• HO2 sensor (bank 2 sensor 2)
• Exhaust manifold (TWC)
ES–257
ES