p0420
Moderate
Lincoln · Sedans
Catalyst System Efficiency Below Threshold (Bank 1)
Quick Answer
Error code P0420 on your Lincoln Sedans 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
Test oxygen sensors upstream and downstream
2
Check for exhaust leaks before converter
3
Measure fuel system pressure
4
Inspect catalytic converter for damage
5
Clean or replace air filter
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 sensors
Engine gaskets
Air filter
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