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Diagnostic code · Emissions

Honda P0430 Code: Catalyst Efficiency Bank 2 (V6)

Updated October 8, 2026Sources

On this page 4 sections
Meaning
Catalyst efficiency below threshold on bank 2: that converter isn't cleaning the exhaust well enough. On a Honda V6, bank 2 is the front bank.
Checks to start with
The bank 2 downstream O2 sensor and exhaust leaks — before the converter.
Safe to drive?
If the light is steady, Honda says to avoid high speeds and have the vehicle inspected immediately. If it starts flashing, stop safely. It also won't pass emissions.

Diagnose before you buy a converter — a worn bank-2 downstream O2 sensor or an exhaust leak can set P0430 even when the cat is fine. On Honda's transverse V6, bank 2 is the front bank (the side toward the radiator).

What P0430 means

P0430 stands for “Catalyst System Efficiency Below Threshold (Bank 2).” It’s the exact same fault as P0420, just on the other bank of a V6. You’ll see it on Honda’s V6 vehicles like the Pilot and Odyssey, not on four-cylinder Hondas. The downstream oxygen sensor on bank 2 is telling the computer that the converter on that side no longer appears to be cleaning the exhaust well enough.

The one thing worth knowing up front: on Honda’s transverse-mounted V6, bank 2 is the front bank — the row of cylinders toward the radiator — while bank 1 is the rear bank against the firewall. Knowing which side you’re working on saves time.

Because a catalytic converter is expensive and an oxygen sensor is cheap, diagnosis order matters: rule out a lazy downstream O2 sensor and any exhaust leak before condemning the catalytic converter on that bank.

Possible causes

  • Failing downstream O2 sensor on bank 2
  • Worn catalytic converter (bank 2)
  • Exhaust leak near the bank 2 sensors
  • Untreated misfire / rich mixture that cooked the cat
  • Aftermarket / non-spec exhaust parts

Do these checks first

  1. Confirm the bank: on a Honda transverse V6 (Pilot, Odyssey, Accord V6, Ridgeline) bank 2 is the front bank, toward the radiator; bank 1 is the rear bank by the firewall.
  2. Read live O2 data with a scanner. A healthy downstream sensor holds steady; if it swings like the upstream one, suspect the converter.
  3. Check for an exhaust leak before the bank 2 rear O2 sensor, since a leak there can fake a P0430.
  4. Rule out the cheaper downstream O2 sensor before condemning the converter; clear any misfire or lean codes first.

FAQ

What does the P0430 code mean on a Honda?
P0430 means catalyst system efficiency below threshold on bank 2. The downstream oxygen sensor on bank 2 is reporting that the catalytic converter on that side doesn't seem to be cleaning the exhaust effectively. It's the bank-2 twin of P0420.
Which bank is bank 2 on a Honda V6?
On Honda's transverse-mounted V6 engines (Pilot, Odyssey, Accord V6, Ridgeline), bank 1 is the rear bank — the row of cylinders closest to the firewall — and bank 2 is the front bank, the row toward the radiator. So a P0430 points at the front bank's converter or downstream O2 sensor.
What is the difference between P0420 and P0430?
They are the same catalyst-efficiency fault on different banks of a V6. P0420 is bank 1 (the rear bank on a Honda V6) and P0430 is bank 2 (the front bank). The diagnosis is identical: rule out the downstream O2 sensor and exhaust leaks before replacing the converter.
Does P0430 always mean I need a new catalytic converter?
No. A worn downstream oxygen sensor or an exhaust leak near the bank 2 sensors can set P0430 even when the converter is fine. Diagnose first — the downstream O2 sensor is far cheaper than the converter.
Can I drive my Honda with a P0430 code?
If the check engine light is steady, Honda says to avoid high speeds and have the vehicle inspected immediately. If the light starts flashing, stop safely. With P0430, the car will also fail emissions, and fuel economy may drop. Pay close attention if there's also a misfire, because an unaddressed misfire is what damages converters in the first place.

Sources

Owner's manual references are to the model and year named above. Wording and procedures can differ on your Honda, so check your own owner's manual.

How we source and correct →