I've read a couple of threads about this issue and have gone through the suggested self-checks:
- check/tighten gas cap
- several drives later, still a solid SES light, no blinking observed

The light came on out of nowhere one day. All stock 05at sedan with low mileage at < 26K.

I'm wondering if there's a place I can get the code checked for free - similar to some auto shops ppl in the states were suggesting. If not, where should I bring it in?

I'm in the GTA as well.

 

Last time this happened to me it was my O2 Sensor. I went to local shops they couldn't tell exactly what it was when they plugged into their universal code reader. I reset my ECU and it would go away for a few days and then come back again. I was forced to go to infiniti for them to tell me what the error code meant and had to pay 1 hour of labour for it (stealership of $119+tax). In the end i bought the part the part from Infiniti and had my local mechanic install it for me instead of another stealership price of $119+tax.