P0430 on a Subaru Outback

What P0430 usually means on a Outback

P0430 is the bank 2 version of the Outback's efficiency code: the catalytic converter on the second bank has fallen below threshold. On the boxer layout the two banks sit on opposite sides of the engine and can age at different rates, so seeing one code without the other is normal. The likeliest cause on a high-mileage Outback is a worn converter, but the same Subaru-specific contributors apply, oil or coolant fouling and lazy sensors. Confirm which side your engine treats as bank 2 before ordering a part.

Most likely causes on this model

1. Worn bank 2 converter

   That bank simply reached the efficiency limit first; common on higher-mileage boxer engines.

2. Oil or coolant contamination

   An oil-burning cylinder or head-gasket seep on that bank degrades its converter early.

3. Lazy bank 2 air/fuel sensor

   A sluggish upstream sensor on that side can misreport and set the monitor.

4. Exhaust leak on the bank 2 side

   A leak near that converter draws in air and fakes a low-efficiency reading.

What it costs on a Outback

As with P0420, the cost gap between OEM and aftermarket converters is the big variable, ranging from a few hundred dollars to well over a thousand installed. If both bank codes are set, budget for two converters. Because Subaru's monitor is sensitive, cheaper cats carry a real risk of re-triggering the code, so weigh that against the upfront savings.

Other codes we cover on the Subaru Outback

Related symptoms

Subaru Outback problems & recalls by year