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2001 Hyundai Santa Fe P0421 Code: Causes, Fixes, and Oxygen Sensor Diagnosis

Model: 2001 Hyundai Santa Fe Fault Code: P0421 Posted: 2008-12-16 20:05

I've been experiencing recurring check engine light issues with code P0421 on my 2001 Hyundai Santa Fe. After replacing the catalytic converter, the code initially disappeared. However, two days later, the warning light returned. I had the code cleared by a mechanic, but it came back again after three days. This is concerning—could faulty oxygen sensors be the root cause? Additionally, when coming to a stop at red lights, my car sometimes feels like it 'jumps'—it doesn't move forward, just seems to bounce or vibrate. The engine runs fine under normal conditions, but P0420 keeps reappearing. I'm looking for reliable advice on diagnosing and fixing this issue. Any experience with similar problems? Thanks. P.S. I reposted this thread as it was initially posted in the wrong section.

Related fault codes

P0421

Comments (3)

Anonymous 2008-12-17 17:40

What type of catalytic converter did you install? A misfire could be causing the P0421 code and may damage the converter over time. The vehicle's vibration at stops might indicate an underlying misfire, which should be investigated.

Anonymous 2008-12-17 22:05

Thanks for the reply. I'm not sure what kind of converter was installed—what are the different types available? And how can I fix a misfire if it's present?

Anonymous 2008-12-18 08:15

There are two main types of catalytic converters: generic 'fits-all' models that cut corners on precious metal content and last only as long as a cigarette, and OEM or vehicle-specific converters designed for your 2001 Hyundai Santa Fe. Generally, you get what you pay for—quality converters perform better and last longer. The vibration during stops could be a sign of misfire; prioritize diagnosing and fixing the root cause before replacing another converter.