P0430: Catalyst System Efficiency Below Threshold (Bank 2)

P0430 is identical to P0420 but on the second bank of cylinders (Bank 2) — it appears on V6 and V8 engines. It means the catalytic converter is not working as efficiently as expected.

Symptoms

Usually a steady check engine light with no obvious driving change, sometimes a slight performance drop or an exhaust smell.

Causes (most likely first)

A weak downstream (Bank 2) oxygen sensor, an exhaust leak before the converter, an aged or failed converter, or poor fuel. Do not replace the converter before ruling out the sensor and leaks.

Diagnosis

Compare the live oxygen-sensor readings on Bank 2 via OBD2. If P0420 and P0430 appear together, the cause may be shared (fuel or an air sensor). Mowtar AI analyses both sensors and ranks the cause.