Emissions

P0430 — Catalyst Efficiency Below Threshold (Bank 2)

Severity: medium Safe to drive

What P0430 means

The engine control unit compares the oxygen sensor signals before and after the Bank 2 catalytic converter. A healthy catalyst smooths out the exhaust, so the rear sensor signal stays steady. When the rear signal starts to mirror the front one, the ECU concludes the catalyst is not working well enough and sets P0430.

Symptoms

  • Check Engine Light on
  • Failed emissions test
  • Slightly worse fuel economy
  • Rotten egg (sulfur) smell from the exhaust
  • Reduced performance in severe cases
  • Often appears together with P0420

Possible causes

  1. Worn out or failed Bank 2 catalytic converter
  2. Faulty or slow Bank 2 downstream oxygen sensor
  3. Exhaust leak near or ahead of the catalytic converter
  4. Rich or lean air-fuel mixture (injectors, MAF sensor, fuel pressure)
  5. Engine misfires that damaged the catalyst
  6. Damaged wiring or connector at the downstream O2 sensor
  7. Oil burning or coolant entering the exhaust and contaminating the catalyst

How to diagnose

  1. Scan all codes and freeze frame data; fix any misfire or fuel trim codes first
  2. Confirm which side of the engine is Bank 2 on your vehicle
  3. Inspect the exhaust for cracks, holes and leaking gaskets
  4. Check the wiring and connector of the Bank 2 downstream O2 sensor
  5. Compare upstream and downstream O2 sensor graphs with a scan tool on a warm engine
  6. Review short and long term fuel trims for a rich or lean condition
  7. Check temperatures before and after the converter; the outlet should be hotter
  8. If sensors and mixture are fine, treat the catalyst as worn out

Common fixes

  • Repair misfires and fuel system problems
  • Replace the downstream O2 sensor if it is faulty
  • Seal or replace leaking exhaust parts
  • Replace the Bank 2 catalytic converter
  • Clear the code and complete a drive cycle to confirm the repair

P0430 on different brands

Ford · manuals
Ford lists the extended code P0430:00 for its gasoline engines as Bank 2 catalyst efficiency below threshold; it reports the monitor result and does not by itself prove the converter has failed.

Questions and answers

Can I drive with a P0430 code?

Usually yes, for normal short-term driving. Don't put it off for long, though, because misfires or a rich mixture can destroy the catalyst and make the repair more expensive.

Does P0430 always mean I need a new catalytic converter?

No. A bad downstream O2 sensor, an exhaust leak or a mixture problem can set it too. Rule those out before replacing the converter.

Why do I get P0430 and P0420 together?

They are the same test run for each cylinder bank. If both are set, look for a shared cause such as poor fuel, a rich mixture or wear on both catalysts.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.