pcpronze Posted July 18, 2023 Share Posted July 18, 2023 Hello I have been a follower of this column for some time and really appreciate the information I can gain from all your experiences. I have a persistent issue with the Jake Brake. Mine is a two stage, low to initiate three cylinders and then, if necessary, the second switch to kick in the last three cylinders. My issue is that it works only randomly when tried. I have taken it to a capable garage that said it was due to the EGR valve hanging and not always making full closure or open. The EGR was changed and I have noticed better speed control on hills. But the Jake Brake does not seem to have improved. I just made a 265 mile trip from Ann Arbor, MI to Petosky, MI. Brake worked every time I put it on going up. Sat for a week headed back south and about one hour into the trip I hit the Jake Brake and it did not come in. So I constantly tried it at every opportunity coming back and it did not work once. The lite on the switch illuminates every time I turn it on but that is the extent of the reaction. This is not the only time this has occurred like this, I am most confident that when I start it up again it will respond perfectly, especially if I make an appointment to take it somewhere. We winter out West and the mountains thru Colorado get darn scary when you hit the switch and nothing happens. Does anyone have a schematic of the circuit so perhaps I could do some trouble shooting when it occurs? I don't know if it is direct link thru the ECM or thru relays. I never get a fault lite or warning just no reaction. Thanks Paul 05 Navigator 1 Link to comment Share on other sites More sharing options...
Jonbrooks Posted July 18, 2023 Share Posted July 18, 2023 The ECM does control several parameters of the ISM engine brake system. There is an oil line under the valve cover that can cause issues as well as the wire harness and connector going into the valve cover. Need to have a shop hook it up to a computer and see if the ECM is getting the high low signal. 1 Link to comment Share on other sites More sharing options...
JJMonaco Posted July 18, 2023 Share Posted July 18, 2023 I had Jake Brake problems on my 2002 Signature coach (ISM 500) similar to yours. It ended up being a bad foot-switch. Check the continuity between the two wires. It should be zero ohms when the switch is on. Link to comment Share on other sites More sharing options...
pcpronze Posted July 18, 2023 Author Share Posted July 18, 2023 I will pull the switch and see what it reads. The shop I had it at could not find an issue when tied to the ECM. Intermittent really is the issue. If when it happens, I could pull over and do some checking without interrogating the ECM it might help. 1 Link to comment Share on other sites More sharing options...
vito.a Posted July 18, 2023 Share Posted July 18, 2023 Do you have both a High and Low Jake brake? Is it intermittent in both? Does it make a difference if the Cruise control is on or off? 1 Link to comment Share on other sites More sharing options...
jfbolkovatz Posted July 18, 2023 Share Posted July 18, 2023 If you have a foot switch to activate the Jake, Change it. In 12 years I'm on my 3rd. Hope this helps. Link to comment Share on other sites More sharing options...
pcpronze Posted July 18, 2023 Author Share Posted July 18, 2023 I have a 1st stage and a second stage which is an addition to the first stage. 3 cylinders when you turn it on and then you can add the second which puts all cylinders in play. First stage must be turned on though. It does not make any difference if cruise is on or off. I have separate switches on the left consul to turn on the brake, no foot switch. Thanks for the input. Link to comment Share on other sites More sharing options...
MHRookie Posted July 19, 2023 Share Posted July 19, 2023 You need to ohm test the switches (both on/off & high/low). They could be the issue. 1 Link to comment Share on other sites More sharing options...
Steven Schoepke Posted July 19, 2023 Share Posted July 19, 2023 Mine 2004 Monaco Executive, the low would work but no high. Turn that the switch on the left control panel had a bad connection. Easy fix after mechanic checked, foot switch, wiring to engine and pulled rocker cover. That was my problem! 1 Link to comment Share on other sites More sharing options...
pcpronze Posted August 7, 2023 Author Share Posted August 7, 2023 Sorry for the long time between post but the coach is not at the house and life in retirement can sure get busy. Back to the subject, I removed the switch and checked the contacts and only got a circuit change of status on one set of contacts that I presume is the light on the switch. I also checked the coach circuit wiring with an OHM meter and found it to have 3K ohm resistance. I ordered a new switch and received it Saturday, installed it today and hope to check it this week and report back. Checking the new switch, I did get two sets of contacts that changed status, so my fingers are crossed. Thanks for the help to this point. Link to comment Share on other sites More sharing options...
pcpronze Posted September 18, 2023 Author Share Posted September 18, 2023 Well we just returned from a trip and I have decided to take the problem of Jake brake to the shop. I had the brake operational part of the time only. When we left it worked about 3 times as I was trying it to make sure that was the problem. At some points it even kicked out when going down a grade. I will see what the shop comes up with. I did see a schematic from a 2003 and it looks like the switch goes to the ECM, but in mine in the driver side electrical relay fuse door below the driver there is a circuit board with a light that says "engine brake OK". I dont see how that comes into the schematic. To be continued. Link to comment Share on other sites More sharing options...
pcpronze Posted February 7 Author Share Posted February 7 Well after further probing I have found nothing. There are two boards in the compartment below the driver that have lights on them but unfortunately you cannot see them when driving and when parked none of the lights come on but should they? It rained one day as we traveled out to Quartzite. The brake worked every time. It was dry coming back and it did not work. So what does that say?? And no, I am not just driving down hill in the rain. The big question is how does this system work? Cummins, after spending $$$ says it is Monaco's design and how it interfaces thru the coach system. So where do you go for a knowledgeable person to talk to or service the unit. Any and all help is appreciated. Link to comment Share on other sites More sharing options...
Ivan K Posted February 7 Share Posted February 7 Just an unverified idea but have you tried to look at the Jake LED while stationary with ignition ON? The decision whether to apply the Jake or not, based on preset road speed, is made in the ECM, so unless there is some other interlock, like maybe Park Brake or gear signal, you might see the trigger going out to the ECM through the Monaco circuits and maybe confirm that part functional, maybe... Link to comment Share on other sites More sharing options...
MHRookie Posted February 8 Share Posted February 8 I need to verify…. Does your Jake brake system have role foot pedal? I just went through some similar issues and it ended up being the micro switch inside the pedal. To test… start coach & let run a bit then….turn on cruise, and select “set” - to enable high idle…. Let it run a min then hit the Jake pedal… it should turn high idle off. See how long the delay is (if any). if it continually turns idle off quickly, then that’s not the issue.. Link to comment Share on other sites More sharing options...
pcpronze Posted February 8 Author Share Posted February 8 I have looked at the light on PCB #8 in front compartment and did not see any lights with key on. But the unit was in neutral with engine off. I tried engine on but still in neutral and had same result. I do not have a role foot pedal only two switches on consul, low must be turned on then high added. There may be interlocks that I do not know about and is why I would like to know how the system actually operates. Thanks for the response. Link to comment Share on other sites More sharing options...
MHRookie Posted February 8 Share Posted February 8 Sorry, didn’t notice the earlier post of no foot switch. The only way I know how to test while stationary is by the high idle. Does your navigator have that feature using the cruise control buttons (make sure engine temp is above 86 deg before activating high idle). aside from that, your going to have to call Holiday Rambler to get the wiring schematics I’m afraid. Link to comment Share on other sites More sharing options...
Yoaks5 Posted February 8 Share Posted February 8 8 hours ago, pcpronze said: I have looked at the light on PCB #8 in front compartment and did not see any lights with key on. But the unit was in neutral with engine off. I tried engine on but still in neutral and had same result. I do not have a role foot pedal only two switches on consul, low must be turned on then high added. There may be interlocks that I do not know about and is why I would like to know how the system actually operates. Thanks for the response. I have the same coach that you do but a different motor. I have 2 switches for the Jake brake one on/ off and the second is high low. I can turn my brake on no matter weather the second switch is on high or low. This sounds different than yours? Also my cruise will not work if the Jake brake is on. If the cruise is on and I turn on the brake it will shut off the cruise like stepping on the brake pedal. I can check the light on the pcb 8 to see if mine is on with the brake if you think it will help or if there is something else I can check let me know. As for the high idle using the cruise buttons. I have to turn on the cruise by pushing the on/off button on the steering wheel then push the resume button to get it to kick up the RPMs. I do have the vorad adaptive cruise on mine. Not sure if any of this helps but I alway figure the more info the better. Link to comment Share on other sites More sharing options...
MHRookie Posted February 8 Share Posted February 8 I did find some other info about the throttle position sensor. If it’s not returning or showing full release, it will keep the Jake brake from engaging. You might look into resetting it, not sure on the type you have. Link to comment Share on other sites More sharing options...
pcpronze Posted February 9 Author Share Posted February 9 Yoaks5 the function is the same as yours and the equipment including Vorad. If you can check PCB8 and see if any engine brake lights are lite up when the key is in on position, engine running but in neutral with brake on, with the first stage initiated. Now the pedal position sensor is another interesting issue. The pedal was changed by Cummins 7 years ago but was or is just as obsolete as the original. Thanks for input. Paul Link to comment Share on other sites More sharing options...
Yoaks5 Posted February 9 Share Posted February 9 See picture. The only light on is the one that says the fuse is OK. It was the same with the Jake brake switch on or off. I'm not sure if it was in high or low on the 2 nd switch. I would guess high since that's where i normally keep it in case i need to stop in a hurry. Motor running, in neutral, brake on. Link to comment Share on other sites More sharing options...
pcpronze Posted February 21 Author Share Posted February 21 I thank all of you for your help in this matter. In going thru the drawings I could find on this site, ones on Ramblin Pushers along with the book of drawings that came with the MH all are lacking and do not contain how the throttle, jake brake and the cruise control are all interconnected. The jake seems to work with the cruise but is intermittent when I actually hit the on switch for the jake. What I am at is does anyone have a possible recommendation of a service place out west. We winter in Tucson, AZ. I will drive to the place that will solve this issue. Going thru the mountains is a lot of work and scary when you are unsure if the brake will come on or if it will stay on. I called REV in Indiana and the tech was honest and said that they had few drawings and no techs of that era. So I am open to suggestions or info to trouble shoot or take the coach to a tech. Link to comment Share on other sites More sharing options...
Frank McElroy Posted February 21 Share Posted February 21 For the engine brake, if you haven't already done so, take a look at page 63 and connector M8. From there you should be able to trace the wiring from the Jake brake switch to the engine ECM. A shop with Cummins Insite software will be able to determine if the engine ECM "sees" if you are activating the jake brake switch. This will isolate the problem to either an input issue to the engine ECM or an output issue from the ECM to the solenoids under the valve cover. If you go to Cummins Quickserve, you should be able to download a wiring diagram for your engine. The Jake brake circuit would be on the OEM side of that engine wiring diagram specific to your ISM-500. Link to comment Share on other sites More sharing options...
Steve Merritt Posted February 22 Share Posted February 22 Paul, I have a 2006 Monaco Executive which is pretty much the same coach mechanically and I had a lot of the same issues you are having including working fine in the rain. I put up with it for over 2 years and spent sadly over $4000.00 at Cummins and other rv shops trying to figure it out. MY culprit turned out to be the front allison transmission speed sensor I was shocked to find out how critical that speed sensor is and it pretty much talks in some way to every component that makes my motorhome move, slow and stop. Something had hit my sensor and cracked it and when it was hot it was apparently opening up and not functioning properly and according to Allison when it was raining the rain being thrown on it from the rear tires was keeping it cool and the crack was staying closed. There are 3 sensors on the transmission but the front one right behind the drive shaft is the most critical and most vulnerable. BTW it on cost me $186.00 for the sensor and everything from the jake brake to cruise control to vorad system has worked flawlessly since I installed to in October of last year. Not sure if this is your problem but thought it was worth mentioning. 1 1 Link to comment Share on other sites More sharing options...
pcpronze Posted February 22 Author Share Posted February 22 Steve Thank You for a direction. I will be under it and see if I can locate the sensors. Would you by chance have a part number? Thanks Frank I just checked and have registered some time ago. I now have a couple of avenues to continue. Link to comment Share on other sites More sharing options...
Steve Merritt Posted February 22 Share Posted February 22 Yes here is my part number and picture of it and my transmission serial data plate you will need your serial number because Allison purged all part numbers pre 2016 and reasigned new ones that are hard linked to serial numbers and that is the only way to make sure you are getting the exact sensor because there are 3 on it about 18 inches apart front to back and all 3 look identical but they internally are definitely not and the closer you get to the engine the more expensive they get for some reason and also none of the new ones have the right angle top they are all straight now. The serial plate is about 6 inches to left and down front the forward most sensor. Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now