Draft guidance: awaiting Claude spot-check, qualified-mechanic review and named-editor approval. Do not use a fault code alone to replace parts.

P0430: Catalyst system efficiency below threshold, Bank 2

The control module believes the catalytic converter on Bank 2 is working below its calibrated efficiency threshold.

What P0430 means

The control module believes the catalytic converter on Bank 2 is working below its calibrated efficiency threshold. Bank 2 is the cylinder bank that does not contain cylinder 1, so the code applies to engines with more than one bank. Left/right or front/rear labels must not be assumed.

Can I still drive?

With a steady light and normal operation, a short, gentle journey can be reasonable, but prolonged use before diagnosis is unwise. Stop for a flashing/red warning, active misfire or shaking, stalling, major power loss, overheating, smoke, strong fuel/burning/sulphur smell, or converter rattle accompanied by poor performance.

Symptoms

  • Often no symptom beyond the warning light.
  • Emissions-test failure.
  • Reduced economy or power.
  • Sulphur-like smell or exhaust rattle.
  • Severe power loss if the Bank 2 converter is restricted.

Common causes

  • Degraded, contaminated, overheated or physically damaged Bank 2 converter.
  • Bank 2 exhaust-manifold, flange, flex-pipe or sensor-area leak.
  • Faulty Bank 2 upstream/downstream oxygen sensor, heater, loom or connector.
  • Misfire or rich/lean running affecting Bank 2.
  • Injector, ignition or airflow/fuelling fault.
  • Oil or coolant contamination.
  • Unsuitable replacement converter or vehicle-specific software issue.

Safe first checks

  • Record all stored and pending codes plus freeze-frame data. Confirm Bank 2 from manufacturer information. Deal with active misfire, fuel-trim and lambda-sensor codes first. On a fully cold exhaust, inspect accessible Bank 2 joints for soot or damage and check sensor wiring for heat damage. Note oil/coolant consumption and previous fuelling faults. Have both Bank 2 sensor traces and converter performance tested before approving a sensor or converter.

Typical UK fix cost

Expect £100–£220 for diagnosis. A leak, sensor or wiring repair may total £180–£500. Bank 2 converter replacement is broadly £650–£2,000 at an independent garage, but integrated or specialist units can cost £1,300–£3,000+. Underlying ignition, fuelling or engine repairs are additional.

Related models

This is a generic OBD-II code used across many makes and models. The exact test thresholds, component layout and repair route vary by engine and manufacturer, so check vehicle-specific technical information before ordering parts.

Related fault codes

Sources

A diagnostic trouble code identifies a system or circuit to investigate. It does not prove that a named part has failed. Preserve freeze-frame data and seek a vehicle-specific diagnosis before clearing the code.