Fast Idle switch Engine Brake

[Zeb Severson]

I have a similar model and year as your coach, but I can't offer help with your issue other than some diagrams.

Here is my engine wiring diagram in Coach Assist:
https://www.beaveramb.org/resources/Documents/Technical%20Forum/Coach%20Assist/Wiring%20Diagrams/2003%20ISL%20Cummins%20CM554%20Caps%20Wiring%20Diagram%203666416%20.pdf

Also in general for your coach, if it is wired like mine, the 2002-2003 Patriot wiring diagrams are incomplete and some additional diagrams can be found in the 2004 Patriot, and the 2003 Marquis diagrams. While not earth shattering information maybe it will help down the line.

I'd also recommend to also sign up for Quickserve with Cummins to access the manuals and diagrams for your specific engine. You might find there is something on troubleshooting the fast idle or possible what the votlatge is for that pin on the ECM.

[Nicholas Soldevere]

Beautiful coach you have Zeb and thanks for the diagram, its a beauty, all the nice colors and lines,, wow!!!  I like it.  I see one there on the far left called Idle Increment/Decrement switch, the drawing doesn't show those switches being on the side console, but I see Eng Brake On/Off and Diagnostic On/Off. Blue line "signal" . Im going to go out on a limb and postulate, that is the fast idle switch and it makes a run to the right to pins 35 and 36, Those pins are shown on a drawing in the book of drawings for the coach, I want to say that plug is C43 but, that would be a guess, I don't have the book in front of me.  I believe that to be a signal line going to the ECM. Anyways, thanks again, I'll use it in the future most likely.