Check Engine Light Due to Gas Cap or Catalytic Converter on Pontiac GTO

A loose or worn gas cap or a faulty catalytic converter are two common items which can cause Check Engine Light to illuminate.

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Average mileage: 106,213 (106,213–106,213)
3 model years affected: 2004, 2005, 2006
4 people reported this problem
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problem details
2004 Pontiac GTO 106,213 mi,
Check engine light came on a few days ago. Got it checked and there was an error for catalyst efficiency below normal.