[77newell]

John: I was just reviewing Chapter 5 of the DDECIV manual regarding cruise control. I'm not sure which version of DDEC electronic engine control you have, but what I've just read convinces me that DDEC itself provides all the cruise control functions. Given your symptoms and my minimal understanding of how the system works the only advice I can offer is that there may be an issue with an input to the ECM or with the ECM itself (less likely I think). A Detroit Diesel shop that works on DDEC engines will have the necessary electronic equipment to determine what is going on.