P0430 on a GMC: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

Drivable in the short term, but the bank 2 converter problem should be checked soon.

What P0430 means on a GMC

On a GMC, P0430 means the downstream oxygen sensor on bank 2 reports the catalytic converter isn't cleaning exhaust as well as it should. It's the bank 2 twin of P0420 and shows up most on V6 and V8 GMC trucks and SUVs.

Is P0430 common on GMCs?

P0430 is a familiar code on higher-mileage Sierra and Yukon models, where converters and oxygen sensors wear with age. Short trips that keep the engine cold can also speed up converter decline over time.

Commonly reported on: Sierra, Yukon, Acadia, Canyon.

Symptoms

Check engine light is on
Reduced fuel economy
Possible rotten-egg smell from the exhaust
Often no noticeable driving symptoms early on

Common causes

most common: Worn or failing catalytic converter on bank 2
common: Faulty downstream oxygen sensor on bank 2
common: Exhaust leak before or near the downstream sensor
less common: Unfixed misfire or rich fuel mixture that damaged the converter

How to fix it

Fix	DIY?	Typical cost
Inspect for exhaust leaks and repair them before replacing anything	Yes	$50–200
Test the downstream oxygen sensor and replace it if faulty	Yes	$60–200
Replace the bank 2 catalytic converter	Mechanic	$600–2500