Shouldn't low FOB battery show up on Dash?

sm1ke

Work In Progress..
Moderator
Contributor
:
Canada
:
'18 CX-9 Signature
But there's a "Battery Dead" warning. Is there a way to detect the key if its battery is dead? (Honest question, there's RFID technology that does not require a power source.) There's got to be a way to know there's a key present to tell you that its battery is dead.
Does it actually say "Battery Dead"? If so, I could see that warning coming up when the fob no longer unlocks the door and you have to use the physical key. Maybe the Battery Dead warning is triggered by the RFID.
 

Avoidin Deer

Zoom Zoom, baby
Contributor
:
Central Virginia
:
2019 CX-5 Reserve
Close, but no cigar. (1995 called and asked me to explain it to you)

There are two independent systems working in your fob.

One uses battery power to 'broadcast' the signal to the car that it's ok to start once it 'sees' that the car is requesting authentication.

The other system uses a proximity RFID chip in the fob that doesn't require battery power.
That's what I was questioning earlier. So you can get a warning light saying Fob Battery Dead because the RFID chip tells the system that there's a fob nearby.
 

Avoidin Deer

Zoom Zoom, baby
Contributor
:
Central Virginia
:
2019 CX-5 Reserve
Does it actually say "Battery Dead"? If so, I could see that warning coming up when the fob no longer unlocks the door and you have to use the physical key. Maybe the Battery Dead warning is triggered by the RFID.
Yeh, it says "Battery Dead" in the 2019 manual.

I'm thinking what you said: RFID sees a key is there, but it's not transmitting. Except RFID does not have that great a range, but I can't think of anything else.
 

wlong01

Patron
:
2019 CX5 Reserve AWD
Think I figured out the problem with the fob.

Went out this morning, fob in pocket, put my foot on the brake, no light on start button. Took the fob out, put it right next to the start button - nothing Then I noticed the brake was locked up tight, pressed the brake hard and felt something like a contact switch, then the green light came on. For some reason in the morning the brake pedal is locked tight.
I'm used to just putting my foot on the brake with light pressure. It's that way all during the day but when it sits overnight the brake gets really tight requiring a lot of pressure to move the pedal. Once it starts the brake feels normal.
 

Avoidin Deer

Zoom Zoom, baby
Contributor
:
Central Virginia
:
2019 CX-5 Reserve
Now you may have another problem, huh?

I've got a Reserve. I use my Parking Brake all the time, and have never had that issue. I'm retired and the car has sat for a couple of days without being driven.

I wonder what's going on...maybe something with the power assist unit?
 
:
2019 CX-5 Sig
OP: Try this next time you get in your car first thing in the morning: don't press the brake pedal and push the ignition switch. If the key fob is being detected, the car won't start but the car will go into accessory mode. If nothing happens, the fob isn't being detected.
 
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