DTC code

P0420: P0420 Diagnostic Guide

Vehicle-specific published guides for this diagnostic trouble code.

P0420 Diagnostic Guide

P0420 usually means the ECM may be seeing low catalyst efficiency on Bank 1.

Article vehicle: 2014-2018 Gmc Sierra 1500 5.3 gas

P0420 may mean the Bank 1 catalyst is not storing oxygen as expected, so the system may consider catalyst efficiency low.

Article vehicle: 2019-2025 Chevrolet Silverado 1500 5.3 gas