Strange Noise in Tow-Haul Mode

[BHenn]

I have noticed a strange noise coming from under the dash of my truck. At first I thought it was one of my after-market gauges on the A-pillar. Now I believe it is coming from under the dash and maybe to the left side of the steering column. I have now determined it only ocurrs while in tow-haul mode. This weekend I would hear the noise and the noise would cease upon turning off tow-haul. Normally the sounds comes while decelerating, best I can tell. The tough part would be to describe the sound. Not a rattle or knock, more of an air leaking noise. A sort of air shutter, sort of similar to the sound of shuffling a deck of cards. That is as close as I can get to the description of the sound. And happening while driving, I can't quite pin-point the location, but my best guess is under the dash. It is driving me nuts! Any ideas???



Thanks,

Brent

 

[JimB1]

Could be electronic waste gate of turbo.

 

[BHenn]

And if it is, is it normal? It doesn't sound normal.....

 

[JimB1]

Only time I've heard it is less than half a minute after cold start-up and it's only about 1 second burst.



Don't have a heavy toy-hauler yet so tow-haul mode doesn't get much use.