Cascadia Warning light

DEF...or your regen and/or exhaust temp sensor is showing excessive temps.

Check you manual or go online for a PDF manual about the "idiot" warning lights on the dash.

 

Here's a link to the Cascadia's Driver's Manual in pdf.

The Idiot light symbols and meanings begin on page 44.

 

Sounds like the warning light for the DPF. Your truck needs a regen.

 

Yeah, it does. Regens are automatic, and the folks at Freightliner I've talked to all mention that parked regens shouldn't start happening until well over 500k miles.

They do have a problem with something called the intake throttle control valve. Looks like a large butterfly plate valve that's controlled by a solenoid. The solenoid goes bad, causing the valve to lock open - and that will prevent an automatic or parked regen from happening.

If you get a check engine lite, or the engine malfunction indicator along with it (and associated flash codes) you'll need to get into a Freightliner or Detroit shop ASAP. Eventually it leads to the engine shutting down.