chestr — If your TCH isn't yet ready to shut its ICE down and go into EV mode, you can force it to do so by taking your foot off the accelerator and briefly shifting into 'B' (it's perfectly safe to do this, even at speed) and then back into 'D' after you hear the ICE rev up ("engine braking"). This procedure will put the TCH into "fuel-cut" mode — the ICE is spinning powered by MG1 with electricity from MG2, but using no fuel — and it will enter EV mode when your speed drops below ~64 km/h (~40 mph).

Stan