Weak Engine Brake on Cummins ISX

its probably your solenoids, or you have an oil pressure problem

 

If the engine brakes work ok when the engine is cold then fade when its up to temp it's likely worn rocker shafts.

 

Give more information. People leave out important details. How long have you had truck? Is this something just happened over night? Important to know becuase 06 Cummins doesn’t exactly have best jakes compared to other motors of that year so maybe you are used to something else. Have a buddy that has an 06 Cummins and deleted the emissions egr crap off it and it was a total different animal and even the jakes

 

Ok this helps. But I can’t help but someone else will. Isn’t 3 stage basically the same as what you are calling 6 stage? 3 stage brake ####### all 6 cylinders
Ps , the word r.e.t.a.r.d gets censored?????
I thinks time for a new trucker forum. What a sensitive liberal website.

 

Wire probably came loose on one of the solenoids. I had same issue with my newest truck with cat. Pulled valve covers and tested the jakes with valve covers off and saw wire was loose. Also fixed a buddies trick with same issue. This wires sometimes need to be pulled off and crimped with a pair of needle nose. I wound up just replacing the harness anyhow but just recrimp and retest with valve covers off

 

If this engine was deleted and they changed turbo you lose the high jake setting on many deletes...