P0430 on a Toyota Highlander

What P0430 usually means on a Highlander

P0430 on a Highlander flags the bank 2 catalytic converter as below the efficiency the ECU expects — a V6-only code, since these engines have two exhaust banks. Just as with the front-bank P0420, the usual story is a worn-out factory converter or a lazy rear O2 sensor rather than an overnight failure. Bank 2 sits against the firewall on these transverse V6s, making it the harder converter to reach and service.

Most likely causes on this model

1. Worn bank 2 converter

   The rear-bank cat on the Highlander V6 loses efficiency with age just like the front.

2. Aged bank 2 O2 sensor

   The firewall-side rear sensor is often original and slows down, mimicking a bad cat.

3. Rear exhaust leak

   Rusted joints at the rear manifold or exhaust pipe admit outside air that throws off the reading.

4. Oil fouling from a sludge-era V6

   An early 1MZ/3MZ that burned oil can contaminate the rear cat over time.

5. Unaddressed rear-bank misfire

   A tired coil on a rear cylinder dumps raw fuel into the rear converter and triggers P0430.

What it costs on a Highlander

The bank 2 converter on the Highlander V6 is the pricier one because it sits against the firewall, adding labor to reach it. Part cost mirrors the front cat, a few hundred dollars for a good direct-fit. Confirm the rear O2 sensor's readings first, since a sensor costs far less than a converter.

Other codes we cover on the Toyota Highlander

Related symptoms

Toyota Highlander problems & recalls by year