Suddenly, out of seemingly nowhere, my 2020 cx5 will not start. I press the ignition bottom, lights come on bright, everything seems fine. I can switch the gears in and out of park with no issue. I try and depress the brake pedal to start the car, but it will not depress.

Battery was changed 3 months ago...i do not know what to do. Thoughts?

 

It still could be the battery. I would try jumping it.

 

Get someone to see if the stop lights are coming on when you press the pedal. If thay don't there may be a wait time with the ignition on to override the start system. Someone else may be able to help with that one.

 

battery is 3 months old, back lights do work fine when pushing brakes

 

The age of the battery does not matter, the first thing based on your description is to double check the battery by way of load testing it. You could at least use a digital volt ohm meter and check the voltage.
Then look at al the cable connections especially the ground cable. they must have good clean contacts.


Note for all reading this:
NEVER assume that just because anyone bought a new battery unless before you left the store or had it load tested there is no way to determines it actual state of health!
There is also for most no way to tell how old the battery actually is unless you decode the serial number on the battery case top itself. Your new battery could be a year or more older than you think it is. New only means new for you.

 

this is a fair point.

Will have somebody check the voltage before i do anything further

 

I will say that this morning it suddenly started with no issues...so i am puzzled

 

That would be a supportive argument to at least consider what I suggested

 

ok , so update.

Tested battery, relay, ensured fobs with new battery....and the verdict is...the starter. Tapped it with a crowbar and on she goes

 

If you can't fix it with a hammer, it's an electrical problem.