Have you updated it since 14E02? That's when I first noticed this change on start-up. And I have an warm-up operating mode you don't list.
You can tell when S1a ends because the ICE begins providing the power needed to propel the car and charge the battery.
Per your stage criteria, S1a ends at the top of my street, perhaps 100 yards away, no more.
- EV power in engage goes to zero,
- charge carat switches from discharge to charge
- engine speed rises and engine is louder, consistent with load.
I'll pay attention on the cold days to see if S1a makes it around the corner. No way I'm near 40C that fast after a -10C night!
And then there's the missing a mode. I would call it "limited EV" mode, characterized by S2 operation, but with a 1-bar ICE threshold that is independent of HVB charge level, but depends on coolant temperature. When using heat, this is the transition mode between S1b and S2, and one that transitions back and forth. As coolant temp falls in a glide, the threshold will drop to 1 bar before dropping to zero (ICE on). As coolant temp rises after a burn, the threshold will rise to the normal SOC-dependent 1-2 bars EV.
Now, if I leave the heat at 60F, this doesn't happen, the car works as you describe. Once I'm in S2, bumping the heat even 2 degrees results in a 1-bar ICE threshold until the engine is warm enough, but it reverts when it cools. It makes for really long glides with a little throttle discipline, and really few EV miles without!