A Loose or worn gas cap may cause Check Engine Light to illuminate.Google+
Car Problem Reports
GMC Sonoma Check Engine Light Due to Gas Cap Issue
GMC Sonoma Problem
Average Mileage: 88,037 mi (42,000 mi - 125,000 mi)
Service engine light keep coming on. We finally just replaced the the gas cap and it took care of the problem!
Visitor, 1996 GMC Sonoma, 125,000 mi
Visitor, 2002 GMC Sonoma, 73,477 mi
Forgot to tighten cap, drew code, tighten cap reset code, vwalla..
Visitor, 2001 GMC Sonoma, 68,750 mi
loose gas cap--engine warnuing light
04/2010 Freeway road was uneven at end of bridge. I hit dip going 60 mph. Truck bottomed out and I nearly lost control. Check engine light came on. I spent $100 to have problem diagnosed as broken fuel cap.
03/14/12 Happened again. 13 reported problems? I think the dealer should refund me the $200 I spent to diagnose this problem.