Jake’s always applied with brake pedal

[Brookhaven66]

Looked at a friends Recently purchased 2001 diesel pusher motor home ism500 Cummins
Spartan/Freightliner chassis,Allison auto trans the other day.
Jake brakes work as should going down the road, the low/high setting seems to work and on/off switch seems to turn Jake’s off. Accept that “anytime” you depress the brake pedal it appears the Jake’s engage, even at idle with parking brake on or off, step on the brake and engine will pop and bang like it’s going to stall, but clears up when you get off the brake. Have to unplug the brake light fuse to remedy this issue or unplugged both air operated brake switches under front windshield coming off of brake pedal valve assembly,either of which disables the coach’s brake lights. No codes on Insite, no Wabco codes, no Allison transmission codes. Also don’t see any data from any module that would lead in any direction. Also this will happen with or without the Jake switch turned in off or on position. The Jake will disengage going down the highway when you flip switch to off position,so I assume the ecm sees the command, but on insite at stop with just key on or even engine running, the insite always shows switch on. I can’t see any other body or chassis modules to communicate with from my nexiq2 data test in 1939 or 1708,
Any advice much appreciated

[Rawze]

Maybe the ecm does not see the tranny is in neutral?. .. that or someone mistakenly set the jakes settings to work, even when trany is in neutral?.

[Brookhaven66]

(12-11-2024 )Rawze Wrote:  Maybe the ecm does not see the tranny is in neutral?. .. that or someone mistakenly set the jakes settings to work, even when trany is in neutral?.

I’ll double check if I can find anything for trans in neutral, But I don’t see anything in Insite to remedy this or the Jake setting, would Calterm be needed to find or change this setting?

[tree98]

(12-13-2024 )Brookhaven66 Wrote:  would Calterm be needed to find or change this setting?

Someone would of had to go in there with c a l t e r m already and changed this parameter(if it exists) I suppose it's possible. Do you have a copy of the program thats in the ECM ? Did this problem start all of the sudden or was it like this when the person bought it?

Also....... are we sure it's the jake brake your hearing and not something else happening that your mistaking for the jake brake? Does insite show jake active at these times?

[Brookhaven66]

Insite doesn’t show its active, or at any % but always shows switch “on” even when it’s off, although while driving switch will turn Jake on or off.
It believe it’s Jake,if you press accelerator to 1500rpm then hit brakes it sounds exactly like Jake,but at idle just sounds worse I think. Can’t imagine what else it could be.
This has been happening since he bought 3 weeks ago.
No help from seller.
Really odd that even on accelerator when you press brake pedal the Jake activates.

[tree98]

You'll need to copy the program out of the ECM with c a l t e r m and have it looked at.

[trucklogger2]

(12-14-2024 )Brookhaven66 Wrote:  Insite doesn’t show its active, or at any % but always shows switch “on” even when it’s off, although while driving switch will turn Jake on or off.
It believe it’s Jake,if you press accelerator to 1500rpm then hit brakes it sounds exactly like Jake,but at idle just sounds worse I think. Can’t imagine what else it could be.
This has been happening since he bought 3 weeks ago.
No help from seller.
Really odd that even on accelerator when you press brake pedal the Jake activates.

Interesting that it activates below the set threshold which is easily set at 8-850 or whatever you prefer and at an idle, try setting idle at 600 and see if it activates then.
You know what I mean below set engine speed where Jake shuts off at…
Would it be possible that switch on pedal is faulty?
What about looking this issue up on expert diagnosis system?