Since the NoWaCa rally in Toppenish a couple months ago, I have wanted to set the Jake Brake for "Auto Cruise Enable" as Mike Young from Cummins Yakima told us a the rally we could do. For those who don't know what this does, if set properly it does two things, as long as you leave the Jake Brake on the "high" setting. First, it engages the Jake Brake on high when the coach is running in cruise control, and speed goes 5 mph over the cruise set speed. When it gets back to target set speed, it stops the Jake braking action and waits till it gets 5 mph over the speed again before reactivation. Second, it activates the Jake when you hit the "Cancel" button on the cruise control, and deactivates the Jake when you hit "Resume" on the cruise control.
I find this to work very well; letting you relax your mind about the coach running up to 70 mph+ when you're going downhill and set for 55 mph, like on I-5 in northern Cal/southern Ore. It's just one less thing to watch. Also, when cruise is on in light to medium traffic, hitting the 'cancel' button gets you slowed down with the Jake when somebody slows down or cuts in front of you, and hitting 'resume' gets you right back to where you were. If you don't care to use either, just leave the Jake Brake on "low" or "off" and it works like normal.
So I really like the feature and those who don't have it (like the way ours came from the factory) might want to have Cummins set it for you through the diagnostic routine on the computer. Cummins Yakima didn't get ours set right and I had to take it to Cummins Renton to get it set right, but they did and it now works well.
On a second thought, Cummins Renton looked at the factory settings on the computer and determined there was what they called a "Celebration" (I think that's the right pronounciation) upgrade available for the ISL 400. Apparently these come out periodically and are software updates to improve the engine/tranny performance. They automatically installed the latest upgrade to our system without asking.
I can tell a difference after this upgrade. I didn't know they had upgraded it until I asked why the coach was running better. The coach seems to have a little more power, is more responsive, idles a little sweeter, and is just more fun to drive.
So, the next time you're at Cummins, you might want to ask about these software upgrades and see if yours is ready for it. It was no extra charge to me but I like the response that came with it.
Former Owner, 2006 36MDDS
2010 Arctic Fox 22GK Travel Trailer
2007 Toyota Tundra