DTC P0420: Catalyst System Efficiency Below Threshold: General Description
The three way catalytic converter (TWC) converts hydrocarbons (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas to water vapor, carbon dioxide (CO2), and dinitrogen (N2).
The TWC efficiency does not depend entirely on engine conditions or the deterioration level of the TWC. It can be optimized by stabilizing the secondary HO2S output.
If the TWC deteriorates, the air/fuel ratio downstream of the TWC (the secondary HO2S output) often differs from the target secondary HO2S output, and the status is represented by the parameter (SIGSQRLS).
Therefore, if the SIGSQRLS exceeds a specified value for a set time, a malfunction is detected and a DTC is stored.
MONITOR EXECUTION, SEQUENCE, DURATION, DTC TYPE, OBD STATUS
| Execution | Once per driving cycle |
| Sequence | None |
| Duration | 50.5 seconds or more |
| DTC Type | Two drive cycles, MIL ON |
| OBD Status | PASSED/FAILED/EXECUTING/OUT OF (TEST) CONDITION |
ENABLE CONDITIONS CHART
| Condition | Minimum | Maximum |
|---|---|---|
| Engine coolant temperature | 156°F (69°C) | - |
| Intake air temperature | -13°F (-25°C) | - |
| Estimated TWC temperature | 806°F (430°C) | - |
| Engine speed | 1,575 rpm | 3,500 rpm |
| MAP value | 27 kPa (7.9 in.Hg, 200 mmHg) | 63 kPa (18.8 in.Hg, 480 mmHg) |
| Vehicle speed | 4 mph (5 km/h) | - |
| Fuel trim | 0.69 | 1.47 |
| Fuel feedback | Closed loop | |
| Monitoring priority | P0456, P0457, P0497 | |
| No active DTCs | P0107, P0108, P0112, P0113, P0117, P0118, P0133, P0134, P0135, P0137, P0138, P0139, P0141, P0171, P0172, P0300, P0301, P0302, P0303, P0304, P0335, P0339, P0443, P0496, P1109, P1128, P1129, P1157, P1172, P2195, P2227, P2228, P2229, P2238, P2252, P2270, P2271, P2646, P2647, P2648, P2649, P2A00 | |