p0420
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Ford · SUVs
Catalyst System Efficiency Below Threshold Bank 1
Quick Answer
Error code P0420 on your Ford SUVs 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
BRNCOBRNCSEDGEESCPEEXPDNEXPLREXPLRHBronco Badlands 2024Bronco Base 2024Bronco Big Bend 2024Bronco Raptor 2024Bronco Sport Badlands 2024Bronco Sport Base 2024Bronco Sport Big Bend 2024Bronco Wildtrak 2024Escape Active 2024Escape Platinum 2024Escape ST-Line 2024Expedition King Ranch 2024Expedition Limited 2024Expedition Platinum 2024Expedition XLT 2024Explorer Base 2024Explorer Limited 2024Explorer Platinum 2024Explorer ST 2024Explorer XLT 2024MACHE
Likely Causes
How to Fix It
1
Check for other DTCs that may indicate an underlying cause
2
Compare upstream and downstream O2 sensor waveforms on bank 1
3
Inspect exhaust system for leaks at gaskets and connections
4
Verify no engine misfires or oil burning are present
5
Replace catalytic converter on bank 1 if catalyst efficiency test confirms failure
Pro Tip
This issue typically requires professional diagnosis. Attempting this fix without proper training could cause further problems.
Parts You May Need
Catalytic converter (bank 1)
Downstream O2 sensor
Exhaust gaskets and hardware
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