p0420
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RAM · Trucks
Catalyst Efficiency Below Threshold
Quick Answer
Error code P0420 on your RAM Trucks means: Catalyst Efficiency Below Threshold. This is usually fixable — see the step-by-step guide below.
Affected Models
Likely Causes
How to Fix It
1
Scan vehicle with OBD-II diagnostic tool
2
Inspect exhaust system for leaks
3
Test oxygen sensors upstream and downstream
4
Check fuel trim and engine fuel mixture
5
Replace catalytic converter if damaged
Pro Tip
This issue typically requires professional diagnosis. Attempting this fix without proper training could cause further problems.
Parts You May Need
Catalytic converter assembly
Oxygen sensor
Exhaust gasket kit
Heat shield
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