A car key light popped back up on my dashboard so me and my boyfriend changed the key battery but the key light is still there ?

I have a Infiniti g35x 2008 and the car runs fine no flickering lights nothing

 

Key light means the iKey system is not recognized by NATS/IVIS. Sometimes fob transponders just die and need to be replaced/reprogrammed by a locksmith with the correct software or the dealership.

There is also an antenna attached to the lock cylinder that can fail.

Troubleshoot the system, section DLK - Door Locks in the FSM.

https://www.nicoclub.com/archives/in...e-manuals.html

 

I changed my key fob batterie recently and ever since then a warning sign pops up on my dash (thats if it detects the key) please help!!!

 

Did you use Energizer battery? If not, then try that first. If no luck then insert the key fob inside the Key Slot that is located below the trunk open switch and see if the light on the dash goes away. If not, then your BCM is going on a very long vacation, you know, the one that it doesn't want to come back from!
I had the same issue with my 07 where the BCM decided to stop powering the accessory relay and therefore it would throw the red light key in my face. I bought a $60 BCM from eBay, used my xTool D7 to program the keys and no more issues.

Guide for Reprogramming Updates to your ECU
See my post #7 where i added power to my broken BCM and it worked but i prefer non-rigged BCM instead.