Illumination of the Check Engine Light can be caused by a loose or worn gas cap.Google+
Car Problem Reports
Saturn Ion Check Engine Light Due to Gas Cap Issue
Saturn Ion Problem
Average Mileage: 85,443 mi (34,000 mi - 173,000 mi)
Visitor, 2004 Saturn Ion, 90,000 mi
Check engine light was on. Got a new gas cap and light went off. Was told it was a vapor leak and could cost $400 to figure out the problem. Thankfully we decided to try the gas cap first. It worked!!
Visitor, 2006 Saturn Ion
My 2006 Saturn ION was showing an check engine light and when I took it to a Saturn dealership they were going to charge me $98 to hook it up and tell me what was wrong. Luckily, I had a friend who had the machine to do this and was able to tell me that it was the gas cap. About a week later the light came on again and since I had problems with the dealership and my oil change I had them check on the light for me and they also diagnosed it as the gas cap. This is twice in two weeks that this light has shown up. I hope this is the last time but I guess we'll have to wait and see.
Visitor, 2006 Saturn Ion, 59,700 mi
check engine light came on last night...my son - in -law pumped gas last and I always click my gas cap several times because I have had this problem before with another automobile....I am glad I read this article here today. I am praying this is all it is. Due mostly to the fact I just found out I need hearing aides and certainly cannot afford any car repairs at this time. Wish me luck I am trying the cap tonight:)
Visitor, 2003 Saturn Ion, 146,020 mi
i bought a 2003 Saturn ION 2 with 143,232 miles on it when i bought it on may 1st,2014. today july 18th,2014 i now have 146,020 miles on it. i drive to work every day about 2-3 miles. i had an air bag light problem. come to find out it was a bad air bag coil or clock spring (horn wasn't working till the air bag coil or clock spring got fixed) now my horn works. i have had my CHECK ENGINE LIGHT come on several times since may 1st,2014 until today july 18th, 2014. one time it came on it was the gas cap. the original gas cap was no good and it needed to be replaced. so i took it to a mechanic and they replaced it with an aftermarket one but it fit my car. anyways 1 week later the CHECK ENGINE LIGHT came on yet again. i went to an ADVANCE AUTO PARTS Store and had them hook up a code reader to it. They did and it came up EVAP System (Small Leak Detected) and me and the advance auto parts employee figured it would be a gas cap so i went back in and purchased one that was Original Equipment Equivelenet and that would fit alot better than my previous gas cap. it did. and still to this day my gas cap is fine because i started my car before i went to work it was fine. i start pulling into my works parking lot and i look at the dash and their is the CHECK ENGINE LIGHT on AGAIN and this is the 3rd Time in 2 Months. while i had the car running (CHECK ENGINE LIGHT IS ON) but, i went and took the gas cap off purposly to see if that tripped the CHECK ENGINE LIGHT. but i went and put the gas cap back on and i tighted it past 3 clicks. i made it 4 clicks and the check engine light never went off. i leave the car for a while and turn it back on again and it didn't work. the light still remained on. i know its not the gas cap but i don't know whats going on with my car. could be a bad sensor or a sensor going. it could be a number of things.
Visitor, 2006 Saturn Ion, 50,000 mi
My mechanic told me it was the gas cap. Ordered a new one (that specifically said it was for my Saturn. Worked for a few
weeks and came back on. I have tried tightening it to no avail. Had car in to fix for recall. They told me they would not
do anything about light. When I got car back light was off. Stayed off for 2 weeks and came back on. Waiting to hear from
my mechanic about what to do. Car is due for inspection.
Visitor, 2007 Saturn Ion, 59,500 mi
If the gas cap is not screwed on tight, the engine light comes on.
seems when I fill up with gas light comes on then after some driving goes off
Check engine light came on. Had it diagnosed at my local repair shop as a loose gas cap. Only costed $14, problem fixed.
Visitor, 2007 Saturn Ion, 90,000 mi
My gas cap had to be replaced too. Engine light came on and auto zone ran the codes for free. Installed the new cap today so hopefully that's the end of that!
Visitor, 2006 Saturn Ion, 79,000 mi
Ditto to what all else have said. It's very annoying.