I stumbled upon this Toyota Yaris thread while researching about toyota engines. It's a very interesting read about DFCO deceleration fuel cut off. Check it out!
Using DFCO to increase your MPG - Toyota Yaris Forums - Ultimate Yaris Enthusiast Site
Quote from the yaris thread:
How can I tell if a vehicle other than the Yaris has DFCO?
Be careful with this test as you may lose Power Steering and Power Brakes during it! Choose the right time and location to perform the test.
On any level or slightly downhill road get up to at least 40 MPH, then start engine braking by keeping the vehicle in gear and letting all the way off the throttle while keeping the clutch disengaged (MT) or keeping the transmission in a gear lower than D (AT). Notice the deceleration force and the sound of the engine.
Now tun off your ignition (This is where you may lose your PS/PB, so be wary!) and watch for any harsher deceleration or change in the pitch of the engine for a few seconds.
If nothing was any different with the ignition turned off then your vehicle uses DFCO. If it decelerated at a different rate or pitch with the ignition off then it does not use DFCO. Do not forget to start your engine back up!