I looked at my FOB and it says 433 so I am going to order the that freq. And yes I am in Ontario in NiagaraI have the same car and the same question; So far, the best cue I found is that the TMPS frequency is the same as the key FOBs. Mine read 433 on the spare key sticker.
The other thing I read was that GM now uses 315 MHz for Bolts in the US and 433 MHz for other locations. (I live in Canada) so, it adds up so far.
I have also called GM and waiting for their call back once they found the answer based on my car's VIN.
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