p0420
Moderate
Opel · Sedans & Hatchbacks
Catalyst System Efficiency Below Threshold (Bank 1)
Quick Answer
Error code P0420 on your Opel Sedans & Hatchbacks means: Catalyst System Efficiency Below Threshold (Bank 1). This is usually fixable — see the step-by-step guide below.
Affected Models
Likely Causes
How to Fix It
1
Verify no active misfires are present
2
Check oxygen sensors are functioning correctly
3
Inspect catalytic converter for physical damage
4
Measure catalytic converter temperature
5
Replace catalytic converter if faulty
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
Oxygen sensor
Exhaust gasket
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