P0430 on GMC
Catalyst System Efficiency Below Threshold (Bank 2)
P0430 on GMC vehicles indicates catalyst system efficiency below threshold (bank 2). Au7o has documented this code across 2 GMC models — most commonly on Canyon, Sierra 1500. 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 GMC range from $400 to $1,500, 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 GMC by Model
GMC Canyon(1 issue)
- P0420/P0430 Catalytic Converter Efficiency Failure (3.6L V6)2015-2022
On the 3.6L V6 (LGZ) Canyon, the catalytic converters lose efficiency and trigger P0420 (Bank 1) and/or P0430 (Bank 2), often a downstream consequence of the engine's PCV-related oil consumption that contaminates the converter substrate and O2 sensors. Both converters can fail around similar mileage since they age under identical conditions.
GMC Sierra 1500(1 issue)
- P0430 — Catalyst Efficiency Bank 2 (Driver-Side) Converter Failure on 5.3L V82007-2018
P0430 is the Bank 2 counterpart to P0420 and, on the Sierra 1500 V8, points to the driver-side (Bank 2) catalytic converter falling below efficiency threshold. The mechanism is identical to Bank 1: the rear O2 sensor voltage begins mirroring the front sensor, so the ECM concludes that bank's cat can no longer store/release oxygen. The specific pattern on these trucks is that the underlying killer is usually AFM-related oil consumption or a lazy/aged rear O2 sensor rather than a defective converter out of the box. Owners commonly report P0430 (or both P0420 and P0430) returning even after installing new aftermarket converters — a well-documented frustration on GM-Trucks and SilveradoSierra forums — because the root cause (oil burning, exhaust leak, or a slow O2 sensor) was never corrected.
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View P0430 across all makes →Frequently Asked Questions
What does P0430 mean on GMC?▼
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 GMC specifically, this code is documented across 2 models.
What causes P0430 on GMC vehicles?▼
Common causes on GMC: 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 GMC?▼
Repair costs on GMC range from $400 to $1,500, depending on the specific model and root cause.
Which GMC models have P0430 documented?▼
Au7o has documented P0430 on 2 GMC models: Canyon, Sierra 1500.