Code reader says that CEL is an EGR issue. Truck drives fine, I was towing with it yesterday, owner is going to take it across 3 states next week. I don't think it should be driven at all until it's fixed, but a new valve is $277 and he was bitching about it. My idea is to remove the EGR valve and soak it down with carb cleaner - if it doesn't work, he's still out $277. I have heard these 6.0's like to fail catastrophically and I'd hate to see this happen to my buddy's truck that we use for landscaping.