Now I'm not to sure how to explain the open and closed loop but I don't think this is normal. It also goes to open loop when your driving and let off the gas, than when you go back right on the gas it takes a second to go back into gear explaining why ppl find the auto tranny horrible.
Someone with more knowledge of this circuit could please chime in here.
In open loop
The ECM is only looking at a few sensors. The sensors it's looking at are coolant temp, intake air temp, throttle position, and manifold air pressure. It looks at those and determines how much fuel is needed based on a preprogrammed map. This is bad for fuel economy and emissions levels. It is also a necessary evil to get to closed loop since the temp of the engine and O2 (oxygen) sensors have to be up to close the loop.
In closed loop.
The computer is looking at all of the sensors on the engine. In closed loop the computer can determine exactly how much fuel is needed to keep emissions down and fuel economy up.
As for the open/closed loop indicator on the ultra gauge showing open while decelerating, that is completely normal for the sonic and any car with DFCO (decel fuel cut off). When you let off the gas while in gear above I think 20mph the ECM turns off the fuel injectors to save fuel. With no fuel the O2 sensors show an extreme lean condition and the ECM would automatically want to add fuel. To eliminate the conflict when the ECM shuts off the injectors it also enters open loop. Once you touch the throttle it turns the injectors back on and goes back into closed loop.
Also on an automatic with DFCO, if the transmission came out of gear during cut off the engine would stall. The transmission stays in gear the entire time the car is moving unless you put it in neutral or come to a complete stop.
