Don't know your model, but I have a 94 F250 460. Almost everytime I work on the passenger side of the engine, usually the plugs, I lose cruise control.

The cause in my case is that my arm bumps the vacuum lines that go to the AC box near the firewall. The vacuum lines are plastic looking things that go into black rubber connectors. The lines are either 2 or 3 per connector. The connector can be unseated enough to kill cruise but not be visibly obvious.

Sooo, go check each vacuum line by hand. It costs nothing to check, takes maybe 1 minute and at least in my case it is usually the cause of non working cruise.

Note that I also occasionally get an engine code set when the connector is off. I do not think the vacuum actually controls the cruise, but it sends a signal to the computer that I think the cruise uses.

Either way it works for me and best of all it is free.

Also check you fuses in the cab and under the hood. Trace all the wires or connections from the cruise controller to make sure they are clean and tight.

Good Luck,

Jim Henderson