P0430 on Subaru
Catalyst System Efficiency Below Threshold (Bank 2)
P0430 on Subaru vehicles indicates catalyst system efficiency below threshold (bank 2). Au7o has documented this code across 1 Subaru model — most commonly on Forester. This code means the catalytic converter on Bank 2 (the side of the engine that does not contain cylinder #1) is not reducing emissions as effectively as it should. The computer compares the readings of the oxygen sensors before and after the converter; if the downstream sensor's signal starts mirroring the upstream one, it indicates the converter is no longer storing and processing oxygen properly. This usually points to a worn-out or damaged catalytic converter, but it can also be caused by faulty sensors or upstream engine problems that have poisoned the converter. The car will generally still run, but it will fail an emissions test. Typical repair costs on Subaru range from $200 to $2,200, depending on the specific model and root cause.
Common Causes of P0430
- •Worn-out or failed catalytic converter (Bank 2)
- •Faulty downstream (post-cat) oxygen sensor
- •Faulty upstream oxygen sensor giving bad data
- •Exhaust leak near the converter or sensors
- •Engine misfire or oil/coolant burning that damaged the catalyst
- •Running too rich or too lean over time
- •Aftermarket or non-compliant catalytic converter
P0430 on Subaru by Model
Subaru Forester(1 issue)
- Catalytic Converter Efficiency Failure (P0420) — Often Triggered by Oil-Burning Contamination2011-2021
Foresters commonly throw a P0420 'Catalyst System Efficiency Below Threshold (Bank 1)' code and an illuminated check-engine light. While the converter itself is the part that degrades, the underlying root cause on FB25 Foresters is frequently the well-documented excessive-oil-consumption defect: burnt oil and unburned fuel coat and contaminate the catalyst, reducing its efficiency until it can no longer pass the downstream O2 sensor's efficiency check. Coolant intrusion and exhaust leaks can produce the same result. Subaru issued a service program (WVI-19/WVI-19R) extending the catalytic converter coverage to 10 years/100,000 miles on certain affected vehicles, and the related Yaeger oil-consumption settlement (2011-2014 models) extended engine warranty to 8 years/100,000 miles.
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What does P0430 mean on Subaru?▼
P0430 stands for "Catalyst System Efficiency Below Threshold (Bank 2)." This code means the catalytic converter on Bank 2 (the side of the engine that does not contain cylinder #1) is not reducing emissions as effectively as it should. The computer compares the readings of the oxygen sensors before and after the converter; if the downstream sensor's signal starts mirroring the upstream one, it indicates the converter is no longer storing and processing oxygen properly. This usually points to a worn-out or damaged catalytic converter, but it can also be caused by faulty sensors or upstream engine problems that have poisoned the converter. The car will generally still run, but it will fail an emissions test. On Subaru specifically, this code is documented across 1 model.
What causes P0430 on Subaru vehicles?▼
Common causes on Subaru: Worn-out or failed catalytic converter (Bank 2), Faulty downstream (post-cat) oxygen sensor, Faulty upstream oxygen sensor giving bad data, Exhaust leak near the converter or sensors, Engine misfire or oil/coolant burning that damaged the catalyst. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0430 on a Subaru?▼
Repair costs on Subaru range from $200 to $2,200, depending on the specific model and root cause.
Which Subaru models have P0430 documented?▼
Au7o has documented P0430 on 1 Subaru model: Forester.