I've got a 99 F250 SD 7.3L. Truck has 161K miles. Today for the first time I'm getting these barely audible warning tones coming from the dash panel. It's a series of 4 tones, about every 15-20mins.

I have no "dummy lights" on the dash and all guages are fine.

Any idea what may be causing this?

 

See your owner's manual under the airbag system.

 

That was it.

Thanks!