Ok, today after school my girlfriend got into her 2002 HD and the light comes on. Once she came to my house I noticed the truck was idling weird. I got in and she told me the light came on after school. While the truck is idling in park, it idles anywhere from 900 to 1300 RPM. It fluctuates sparadically. While in drive, it is idling at about 1000 still fluctuating. Any ideas? I know it could be a hundred different codes just wondering if anyone has had this problem. The truck just hit 10,000 miles. Thanks in advance. Dale

 

hmm, not sure what it may be, so hopefully one of the other guys will be able to help you out, but welcome to the site!!!

got any pics of your truck? and what build#?

 

Check the gas cap! If the cap is not secured properly, it will cause this type of symptom since the tank is a pressurized component of the entire fuel system. Give it a try! ... bet the light goes out and she "settles down" to a nice even purr!