CM 870 JAKE BRAKES

[Catman]

CM870 s/n 79022376
We have just recently rebuilt the engine and it has less than 10,000 miles on it. The engine runs good and strong as a rebuilt engine should. Within 3,000 miles the Jake would very intermittently act like one cylinder had the Jake stick on after using high Jake. It would only happen if the truck was loaded. Can never get it to happen when the truck is empty. All injectors are new and we installed reman rocker assemblies both valve and injector. Installed a new valve cam and reused the injector cam. Have rechecked all overhead settings and base trimming. Have performed a injector leak test with no bubbles. Have been running truck without using the Jake and had no problems. Started using the Jake the other day to try and get the problem to happen so I could figure the problem out. Now when we operate the Jake we only get low Jake. Used my scan tool and it shows all three positions of the switch. Checked internal harness and the two Jake solenoids and they checked good. Pushed buttons on solenoids and both are working. I am only getting 12 volts from the ecm to the rear solenoid. Spooned into pin 31 at the ecm for the front solenoid and never get voltage no matter what position the switch is at. This truck also has had a active fault for the EGR for the entire 2 years we have owned it. I was wondering what was found with this other truck to fix the low Jake only problem. The description of that truck seems exactly like what I have going on.