p0420
Moderate
Porsche · Sedans & Sports Cars
Catalyst System Efficiency Below Threshold Bank 1
Quick Answer
Error code P0420 on your Porsche Sedans & Sports Cars means: Catalyst System Efficiency Below Threshold Bank 1. This is usually fixable — see the step-by-step guide below.
Affected Models
Applies to all models
Likely Causes
How to Fix It
1
Scan for pending codes and read freeze frame data
2
Inspect exhaust system for leaks before the catalyst
3
Test upstream and downstream O2 sensors with a scope
4
Measure catalytic converter temperature and efficiency
5
Replace catalytic converter if efficiency is below specification
Pro Tip
This fix requires some technical knowledge. If you're unsure about any step, consider contacting support or a qualified technician.
Parts You May Need
Catalytic converter assembly
Oxygen sensors (upstream and downstream)
Exhaust gaskets
Heat shielding
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