P0420 Diagnostic Trouble Code Discussion for September 2026
Catalyst Efficiency Below Normal (Bank 1)
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| Help Request | Posted | |
| 2016 Cadillac Escalade ESV Platinum 6.2L Excessive Emissions, Poor Idle Quality, MIL Lamp on VIN: 1GYS4KKJ9G P0420: Catalyst efficiency below threshold Bank 1. **Repeat P0420 and persistent negative Bank 1 fuel trims after AFM delete** Greetings, This is a 2016 Cadillac Escalade with a 6.2L L86 engine and approximately 158,000 miles. The customer first brought it to us for a pre-purchase inspection. It ha... |
September 21, 2026 |
