There is a warning light that looks similar to the key warning light.
Are you seeing this? If so, it's a system warning. I got it after changing the low voltage battery in my car. I took it to the dealer - they said my gas cap was loose (didn't seem likely), but the light was gone when I left the dealer.
2015 QX60 - I am looking on here for help with my key fob low battery alert. It is only one of my two key fobs. Husband's works but mine causes the low battery alert to go on for a few minutes after starting the car. It doesn't stay on. I have changed the battery twice. I have cleaned out the fob it self of dust, made sure the connections are clean - no delay in starting I just get the warning everyday. It's the main fob that I have used for the last 5years, do they just get worn out?? Thank you