Re: Malfunction Light
I recommend to anyone that owns a modern vehicle to invest in a code reader. They are not expensive (under $50 at Walmart), and will let you read the code that generated the Malfunction Indicator Light (MIL), take remediation action, and clear the code yourself. While the terminology used for each of the codes can be very confusing when trying to figure out what it is trying to tell you, a brief search on the Internet using the code and/or description will usually give you several things that might be causing the problem. Even if you don't want to try to fix it yourself, at least you have some idea of what the truck thought was wrong before you take it in to the dealer.
... and if you decide you don't want to fix it yourself, then don't clear the code -- the mechanic needs it.
My $80 code reader (bought several years ago when they were pricier) has saved me well over $2000 so far in simple stuff I could fix myself.