Catalyst System Efficiency Below Threshold (Bank 1)
| Code | P0420 |
| Description | Catalyst System Efficiency Below Threshold (Bank 1) |
| Possible Causes | The catalytic converter efficiency has dropped below the acceptable threshold. Most common cause: worn catalytic converter. |
| System | Emission Controls |
Catalyst System Efficiency Below Threshold (Bank 1). This diagnostic trouble code (DTC) is stored when the vehicle's onboard computer detects an issue with the emission controls.
P = Powertrain code
0 = Generic (SAE standard)