P0420 Diagnostic Trouble Code Discussion for June 2026
Catalyst Efficiency Below Normal (Bank 1)
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| Help Request | Posted | |
| 2007 Chevrolet Silverado 1500 LTZ 5.3L Poor Idle Quality, Hesitation, Misfire, MIL Lamp on VIN: 2GCEC13J37 P0420: Catalyst System Low Efficiency (Bank 1). this is an intermittant misfire. #3 cylinder counts misfires only at idle in gear. in the misfire history #6 shows 21k misfires, but havent seen it mis a beat since it arrived. cyl#1 18 misfires #2 9528 #3 2663 #4 599 #5 2 #6 20917 #7 3 #8 956 when driving... |
June 26, 2026 |
