[Phantom]

Most if not all GM have DFCO but the settings are not set the best on the vehicle. My 03 Grandprix can go into DFCO much easier than my 98 Bonneville both have the same settings for DFCO but the Bonneville has taller gears so I'm not always above the needed RPM to enable DFCO when letting off the gas.

If you can see when the vehicle goes in to closed and open loop then look for that if going down a hill and the throttle is at 0% when doing 65mph after 2-3 sec the PCM should go into DFCO if the revs were high enough to the gear. If it does not go into DFCO (indicated by open loop) try again and down shift this time and see if it happens.