Illumination of the Check Engine Light can be caused by a loose or worn gas cap.Google+
Car Problem Reports
Cadillac CTS Check Engine Light Due to Gas Cap Issue
Cadillac CTS Problem
Average Mileage: 76,349 mi (11,872 mi - 180,000 mi)
Visitor, 2006 Cadillac CTS, 38,618 mi
Cap was loose and caused check engine light. When tested error read as some kind of leak. But, all was needed was to tighten the gas cap and have the error message removed.
Visitor, 2003 Cadillac CTS, 119,000 mi
same problem with my car check engine light due to gas cap
Visitor, 2007 Cadillac CTS
at 48000 miles the check engine light has come on 3times the the car dealer replaced a sensor to the gas tank and it came back on. The GM dealer said it was the wire to the sensor. A week later it came back on. They spent 4 hours trying to figure it out. They reset it. Now at 54000 miles it is on again. I am thinking somebody at on star is putting the light on. I had simular problems with my 97 catera oillight. And now my warranty is done. The front passanger shock is making noise. The auto trac and auto stablization is out of control.
Visitor, 2003 Cadillac CTS, 64,000 mi
Ive been having the engine light stay on now.........changed the gas cap.. still on.... 2003 cts v6
Visitor, 2011 Cadillac CTS, 32,000 mi
c-1 coil gone already ??
Visitor, 2003 Cadillac CTS, 92,000 mi
Ingine light came on and I had it checked for free at NAPA and was told that probably the gas cap not sealing correctly and to replace this first...... Replaced the cap at a cost of around $8 and that fixed that problem... By the way NAPA had the replacement cap right there in their store... No service charge just the purchase of the new gas cap... Problem fixed and light off!
Visitor, 2003 Cadillac CTS, 85,000 mi
I replaced the gas Cap and corrected the problem.
Visitor, 2003 Cadillac CTS, 76,139 mi
the gas cap msg has come one twice since I bought the car just over 60 days ago. I've had no other problems with it till now. Now the check engine light is on
126000 miles when problem started
Visitor, 2009 Cadillac CTS, 45,000 mi
Too lazy to buy another gas cap, doesn't seem to effect much, just an annoying light.