Ddec III cruise troubleshooting

Ok, 2 things. One could be the brake pressure switch. Mine was faulty and occassionally the cruise wouldn't work. But the Jake wouldn't either.

Another issue could be in the ECM. Mine does the exact same thing now. Fast idle works, but cruise doesn't. The ECM went bad and the new one was not able to be flashed from the old. Detroit set the parameters as it was delivered from the factory. They, Interstate Power Systems told me the fan settings and the cruise control are set by Kenworth. Perhaps yours has been replaced. If you are near Effingham, The Diesel Doctor says he knows what to do to get it to work.

 

I fully recommend DCS - Fernando - for Detroit ECM. He gets into them and test benched them.

E-ham D.Doc is just a laptop guy, and not a mechanic. Ok for parameter changes, but doesn’t understand Diesel engines.

Not bashing, just from what I’ve learned so far.

 

I agree. In my situation it is strictly parameters.

 

On detroits you can enable/disable cruise but only using DDRS not DDDL.

From what it sounds like your park brake doesn't change function but everything else works.
Park brake should be an air switch rh side on the steering column. If you have opti idle park brake circuit also goes through neutral safety and hood tilt switch.

If it revs up idiling it must see park brake as "on". Get it to read the opposite then take it for a spin.

If the engine sees a ground on the park circuit that counts as parked. Open circuit is not parked.

 

I knew you could explain it better.

 

There may be 2 or 3 park brake switches by the steering column. One for daytime running lights, one for fan on with park brake, and one for ddec signal