379 engine brake

I'm assuming that you had high engine brake before. If that is the case then the first thing i would look at would be the selector switch in the dash. On a cat c-15 the engine has 3 jake heads. On low only 1 head is functioning. On med the other 2 heads are functioning. On high all 3 work together. The only way for all three to not work but work independently is the engine ecm is not seeing ground on both the low and med jake inputs coming from the switch in the dash. Verify continuity through the switch on all pins and i bet you'll find your problem. Hope this helps.

 

Did you get it fixed. Mine is only working on Med. No low or high

 

Check the switch to make sure there is no chaffed or broken wires first. If everything checks out i would pull your valve covers. They are notorious for the wires to come out of the connectors or break due to alot of vibration. If you have to replace the wire be careful not to drop anything in the head. That is the two first steps i would take bud