P0430 moderate

Catalyst System Efficiency Below Threshold (Bank 2)

What does P0430 mean?

The P0430 code means the vehicle's onboard diagnostic system has detected: Catalyst System Efficiency Below Threshold (Bank 2). This is a moderate severity code.

Common Symptoms

  • Check Engine Light on
  • May fail emissions test
  • Possible sulfur smell in some cases
  • No noticeable drivability issues

Probable Causes (Ranked by Likelihood)

  • Failed Bank 2 catalytic converter Very High
  • Faulty downstream O2 sensor on Bank 2 High
  • Rich-running condition on Bank 2 overheating the cat Moderate
  • Oil or coolant fouling the Bank 2 catalyst Moderate

Step-by-Step Diagnostic Procedure

  1. Compare downstream Bank 2 O2 sensor waveform to upstream. Downstream should be slow and lazy.

  2. Replace the downstream O2 sensor on Bank 2 before replacing the cat if it is over 100,000 miles.

  3. Check for exhaust leaks and oil consumption.

  4. Perform a temperature delta test across the Bank 2 converter.

Frequently Asked Questions

Do I need to replace both cats if I get P0430 and P0420?

Not necessarily at the same time. Diagnose each bank independently. If both are failing simultaneously, suspect a root cause (rich condition, oil consumption) before replacing both converters.

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