p0420
Moderate
Skoda · Sedans & Hatchbacks
Catalyst System Efficiency Below Threshold (Bank 1)
Quick Answer
Error code P0420 on your Skoda Sedans & Hatchbacks 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
Verify catalytic converter temperature using infrared thermometer
2
Test upstream and downstream oxygen sensors
3
Check for exhaust leaks with soapy water
4
Perform fuel system pressure test
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 (if faulty)
Oxygen sensors
Infrared thermometer
Fuel pressure gauge
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