2009 Freightliner Cascadia

Hey guys. I got a question. I have 2009 Freightliner Cascadia. Smartshift transmission. Had thus truck for 3 years already. Just recently some odd stuff started happening. As I'm going loaded or empty through Montana or south Dakota or any state with mountains I get this weird check engine light on and my truck begins to loose power. RMP's start dropping. Like I said...it doesn't matter if I'm empty or loaded. Every time I go up the mountain it starts happening. I've tried countless amount of times to park my truck asap and check for the codes and faults but,,,, as soon as I let go of that gass pedal those check engine lights go out. And 2 min later (it's different every time) lights come up again and I'm forced to downgrade in gears to keep going. Note: it never does that when I go down the mountain or on the straight road. Sometimes it does it even when I drive a bobtail up the Idaho pass on i90 or the one in Butte Montana also on i90. Any help please...I don't know what to do because I get no codes or any faults. Tried hooking up computer many times but computer shows no problem at all and no codes. What can it be?

 

I'm an owner opalko. Bro

 

I'm an owner operator.