DTC P0420 Catalyst System Efficiency Below Threshold (Bank 1); DTC P0430 Catalyst System Efficiency Below Threshold (Bank 2): Description
The ECM uses sensors mounted in front of and behind the three way catalytic converter 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 while performing active air fuel ratio control, rather than the conventional detecting method, which uses the locus ratio
The oxygen storage capacity value is an indication of the oxygen storage capacity of the three way catalytic converter 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 heated oxygen sensor is long, the oxygen storage capacity becomes greater There is a direct correlation between the oxygen storage capacities of the heated oxygen sensor and the three way catalytic converter
The ECM uses the oxygen storage capacity value to determine the state of the three way catalytic converter. If any deterioration has occurred, it illuminates the MIL and sets a DTC
| DTC No. | DTC Detection Condition | Trouble Area |
|---|---|---|
| P0420 | Oxygen storage capacity value smaller than standard value under active air fuel ratio control (2 trip detection logic) |
|
| P0430 | Oxygen storage capacity value smaller than standard value under active air fuel ratio control (2 trip detection logic) |
|
HINT
- Bank 1 refers to the bank that includes No 1 cylinder
- Bank 2 refers to the bank that does not include 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