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I have only anecdotal evidence but I suspect the ICE kicks in at -15c as read by the ambient temp sensor.

I park in a heated garage over night and my fluid temps and ambient temp read 20c when I get in.

This past week we experienced some low temps (down to -28c one morning) I noticed that I could drive in electric up until my ambient temp sensor read~-15c. Even though the battery temp would have been higher and my fluid temps had dropped to about 10c.

Add to this if I park the vehicle but keep it running my ambient temp sensor is tricked as I have a winter front installed and the ICE heats the engine bay and ambient temp sensor up above -15c.

The ICE will shut off at this point so long as I don’t have the heater on high heat and high fan speed (turning the fan speed down in this scenario appears to reduce load on the system to the point the ICE is not needed).

Maybe this will help give you some critical points to look for, I don’t have a PID reader.

FORM also kicks in more often in the cold mostly due to oil refresh - like you said though, this is completely normal and I really suggest people just let it run its course. Read up from last year, some people figured a way around it by just resetting the oil life and… their story didn’t end so well. Try smelling the dipstick when FORM kicks in, you may smell a bit of fuel in the mix :)
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