A loose or worn gas cap could be cause the Check Engine Light to illuminate.
Car Problem Reports
Cadillac SRX Check Engine Light Due to Loose or Worn Gas Cap
Cadillac SRX Problem
Average Mileage: 76,400 mi (60,000 mi - 105,000 mi)
Visitor, 2005 Cadillac SRX, 82,000 mi
2005 SRX V8 AWD engine light came on after a fill up and noticed the gas cap felt loose (not ratcheting to a tight fit) After looking at various website threads I made mistake of buying a generic Stent brand cap. Not only didn't the rubber tether fit this cap but engine light still on. Ordered the correct cap from gmpartsdirect.com, installed and engine light went out within 10 miles of driving.
Visitor, 2004 Cadillac SRX, 60,000 mi