P0430 on a Toyota Highlander
P0430 means catalyst System Efficiency Below Threshold (Bank 2). On the Highlander, a few causes come up far more than others.
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 common causes on the Highlander
- Worn bank 2 converter
The rear-bank cat on the Highlander V6 loses efficiency with age just like the front.
- Aged bank 2 O2 sensor
The firewall-side rear sensor is often original and slows down, mimicking a bad cat.
- Rear exhaust leak
Rusted joints at the rear manifold or exhaust pipe admit outside air that throws off the reading.
- Oil fouling from a sludge-era V6
An early 1MZ/3MZ that burned oil can contaminate the rear cat over time.
- Unaddressed rear-bank misfire
A tired coil on a rear cylinder dumps raw fuel into the rear converter and triggers P0430.
What P0430 costs to fix 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.
Year, engine and mileage change the answer. Start a case and Redline weighs these causes against what your car shows, then names the check that would settle it.
Other codes on the Toyota Highlander
Related symptoms
Toyota Highlander problems & recalls by year
Based on widely reported patterns for this model; individual causes vary by year, engine and history. Generic P0430 behavior is covered on the main P0430 page. Confirm with a scan tool before buying parts.
P0430 on your Highlander?
Every problem becomes a Case. Tell Redline what your Highlander is doing: it shows what the evidence supports, what’s still missing, and what to check next, before you approve a repair.
“Inner pad ~1 mm. Outer pad 3 mm.”
Next: check the slide pins move freely before buying parts.