Cruise Control Operating Jake, A Great Feature

[Lug_Nut]

Well, for ever I have thought that the Jake would not operate if the cruise control was enabled. Wrong! At least on mine and all other K-2, K-3 and probably Mountain Master Spartan chassis too.

So, for those, like me that believed it does not work with cruise, check this out.

I have the two speed Jake, "Low & High". This gives me 3 slowing features as follows.

* Low Jake and downshift
* High Jake and downshift
* Downshift only (with Jake off)

The Cruise control, via the ECM uses 5 slowing features as follows

* Low Jake with no downshift
* High Jake with no downshift
* Low Jake and downshift
* High Jake and downshift
* Downshift only (with Jake off)

Here's how it works. This feature is probably most useful on a hilly or mountainous interstate, not a windy switchback. This is due to the over speed.

Engage the cruise control at the desired road speed. Turn the Jake "On". Now you come to a long downhill grade. The coach starts picking up speed, no action yet. At about 5 MPH over your set speed you will notice your auxiliary indicator light illuminate and a very slight forward rolling resistance. The shift pad indicator will remain "6-6" with no command to downshift. Two things have happened. The ECM has shut the fuel flow off to the engine and has engaged the Jake alone. If the coach continues to accelerate, at about 8 MPH over your set speed the ECM will activate the transmission downshift. The ECM will now monitor the vehicle speed and will automatically shift between Low and High Jake as needed. When you reach the bottom of the grade and the speed bleeds off the near the set speed, the ECM will disengage the jake, turn on the fuel, and turn the thottle control back to the cruise setting.

This is SO SMOOTH. Far smoother than you could do it manually. Additionally, the starting of the Jake first then later the downshift, makes it seamlessly smooth. It works excellent.

So, if you did not know about this, give it a try and if you did, how come nobody told me?

Peter

[soricobob]

I thought everyone knew this.

[afrank1971]

Yes, I agree, this is a great feature! And I believe it is actually a Cummins feature. I don't believe it is chassis specific, but engine specific. Not sure at which level of engine they add that feature, but mine is an ISL and it has it.

[footdoc]

what about on mine..I have low/off/high jake switch...no seperate on/off switch.. 06 Mountain Aire

[EngineerMike]

The Jake interaction w/the cruise control is settable in the ECM programming. Jake can be either activated to work w/CC or inactivated when CC is "set" (as opposed to ON).
Our 06 coach had Jake inactive when CC was set. 08 has Jake active in CC mode, which I like mo bettah. If you have one mode and want to switch, anyone w/Cummins Insite (scantool) or Insite Lite can reset it the other way.

[69RoadRunner]

I haven't noticed it kick in on mine. I'll set the cruise at 65 and it I've seen it go up to 72. I haven't done any big hills yet.

[SX_RVing]

Peter,

I had noticed some of the features as you describe.

However, on our Essex, when the jake is set to low, on a long downhill grade, the jake will come on, and if the speed continues to increase, then I'll get a check engine warning. If I put my foot on the brakes, or switch to high jake, the warning will shut off. It's done this since day one. I've talked to Spartan about this, and they are at a loss to explain the code.

Maybe the ECM needs to be re-programmed? Any ideas?

Thanks

Sebastian

[Lug_Nut]

That's a puzzler. If Spartan can not figure it out, it's doubtful we can shed much light on that. Your RPM when this happens, is less than 2500?

Peter

[afrank1971]

Footdoc, mine is the same way. No on/off switch, just hi or low. It works together with the cruise control whether switched to hi or to low. I always just leave it switched to low. I also had Cummins reprogram the Jake to activate with the brake rather than activating when you let off the accelerator. I believe you and I have discussed that before and you already have yours set that way. That too is a GREAT feature.

[SX_RVing]

Quote:

Originally Posted by Lug_Nut That's a puzzler. If Spartan can not figure it out, it's doubtful we can shed much light on that. Your RPM when this happens, is less than 2500? Peter

Peter,

RPM is typically 2200 - 2300 rpm. The code indicates something about turbo outlet pressure. No one seem to know why this warning occurs. Only happens with cruise control, low jake, on long downhill grade. Beats the heck outa me!

Sebastian

[read & learn]

On our 05 KSDP it lets the speed increase 5/6 mph than holds it at that speed on 5% grades or less. Over 5% we have to watch as the speed does start to increase.
This feature has made traveling out west a lot nicer on "them there hills."

[TheJazzMan]

Quote:

Originally Posted by SX_RVing However, on our Essex, when the jake is set to low, on a long downhill grade, the jake will come on, and if the speed continues to increase, then I'll get a check engine warning. If I put my foot on the brakes, or switch to high jake, the warning will shut off. It's done this since day one. I've talked to Spartan about this, and they are at a loss to explain the code. Maybe the ECM needs to be re-programmed? Any ideas? Thanks Sebastian

...just thought I'd chime in with a "me too" comment. The check engine light on my '09 Essex came on while descending a long steep grade with the engine brake on high - scared the %$*& out of me.

Thanks, Peter. I didn't know that the engine brake worked with cruise on. I'll try it on my next trip to the mountains.

[SX_RVing]

Quote:

Originally Posted by TheJazzMan ...just thought I'd chime in with a "me too" comment. The check engine light on my '09 Essex came on while descending a long steep grade with the engine brake on high - scared the %$*& out of me.

I know that feeling well. Have to stop and change your shorts when it happens!

Sebastian

[Radioman]

SX_RVing & Others

Would love to use this feature but have a similar check engine light problem. Comes on when Jakes on low or hi going down hill but my fault code is #143, Low Oil Pressure. Cummins shops in Cinci and Ocala (where we lost 3 days as they tried to diagnose the problem) could find no oil leaks or other problems though Ocala replaced one of the entire Jake assemblies just to make sure. I spoke directly to Cummins engineers and Jake engineers & finally a Cummins regional trouhleshooter said the engine computer had to be reconfigured somehow. Had that done last week at Cummins in Elkhart. That should fix it once & for all they said.

Coming down the hills approaching Des Moines yesterday, guess what? Yup, engine warning buzzer and light came on again! Driving me nuts!!

Will call Cummins factory again tomorrow and sure hope we get this resolved. I doubt any harm is being done - Jake & Cummins people said they thought the same, but of course could not GUARANTEE that. . .

Anyone have any ideas? SX_RVing, did you ever get your similar probvlem resolved?

Once this is fixed, I want the combo Jake/Cruise setup described in this thread. Does anyone know if it's already on 450 ISMs in 08 MADPs?