Hi Pete,
Did you ever solve this? I've developed the same intermittent code 24 error. My ECM is not putting out a 12V signal on circuit 437 , speedo works but cruise control doesn't.
I've replaced the speed sender just before this happened. I checked delcowizzid's suggestion and checked the continuity between A10 and the green wire at terminal K on the cruise control= zero ohms so that total circuit seems OK.
I recently fitted a MACE chip - could that do this somehow?
I'm open to any suggestions before I replace the ECM.