p0420
Moderate
Ford · Sedans & Cars
Catalyst System Efficiency Below Threshold (Bank 1)
Quick Answer
Error code P0420 on your Ford Sedans & 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 vehicle diagnostics
2
Check oxygen sensor signals
3
Inspect exhaust for leaks
4
Monitor catalyst efficiency
5
Replace catalytic converter if needed
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 (optional)
Oxygen sensor (optional)
Exhaust gaskets (optional)
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