Engine Drops To 2000 Rpm No Matter What

[Blastfurnace]

Hello,

 

My Dad has a 2004 Silverado Diesel 2500HD with the Allison Tranny.

 

He is having a recurring problem with the engine. He will be driving and it just drops to idle engine speed and nothing will get it above 2000RPM.

After you park it for a while and restart it you can drive it just fine but then you never know when it will do it again. Which is really scary if you are tooling down the highway in traffic and the engine just goes into idle.

 

No lights no warnings, no check engine, nothing. Just idle.

 

Any ideas?

 

Thanks

 

Mark

[2500HD_DirtyMax]

sounds like it is going into limp mode, the strange thing is that limp mode is supposed to be a fail safe after a major code is thrown. mine used to do it all the time when i was pumping 600hp thru the stock tranny. it would trip the check engine light and enter limp mode. i would have to clear the codes before it would run right. it would also display reduced engine power on the dash display.....

I have never seen one enter limp mode without throwing a code!!!! sounds kinda weird

[8100 Power]

Fuel filter.