Modern cars are full of electronics, and a key fob is no exception.
Inside, it has an electronic chip that works as a transmitter; it
transmits the signal when you press the button to open the
door.
The key fob is powered by a little battery. The battery may last
for 2-3 years in a smart key fob and for 4-6 years in a regular fob
with the key.
The reason for this difference is that the smart key fob also has a
receiver and has to communicate with the car more often when it's
inside or near the car. In most cars, a key fob battery is not
rechargeable, and must be replaced once it loses its charge.
What are the signs of a weak fob battery? As the
fob battery becomes weaker, the transmitter loses its range. This
means that you have to be closer to the car for the fob to work. In
cars with a push button start, a vehicle may not always recognize a
smart key fob in your pocket or purse if the fob battery is weak.
In some cars, a warning message "key fob battery low" may also pop
up on the driver's display.
Will the car start if the fob battery is weak? In
most cars, the security (immobilizer) chip inside the fob works
without a battery, but only from a very close range. So even if the
fob has a weak battery, it should still start the car. You may have
to hold the smart fob closer to the "Start" button or insert it
into a special slot to start the engine. Check your owner's manual
for directions. A conventional mechanical key might also be stored
inside the fob. This key can open the driver's door in case the fob
battery is dead or if the main battery in a car is discharged.
How can you check the fob battery? In many cars, a
key fob has a
G4 vore that illuminates when pressing any
of the fob buttons. If the LED light doesn't light up at all, the
fob battery is dead or there is some other problem with the fob. If
you already have the fob battery out, you can check its voltage
with a voltmeter. The voltage is marked on the battery.
Seduce me gif This battery is
bad, as it only shows 2.858 Volts. A good 3-Volt battery should
show a little more than 3 Volts.
If it's a 3-Volt battery, and it shows less than 3 Volts, it's
weak. For example, this 3-Volt battery in the photo shows only 2.8
Volts; it's bad and must be replaced.
What kind of a battery does a key fob take? Different cars use
different batteries. The most common types are CR2025 and CR2032
3-Volt batteries. You can find the exact type in the owner's
manual. Batteries like this are sold in any electronics store or at
a dealership.
Changing the fob battery is not very difficult. Check the owner's
manual for the instruction and precautions. There are plenty of
Youtube videos on how to do it too. You might need a small flat or
Phillips screwdriver.
For example, to open the key fob in the top photo, we pried it open
with a little flat screwdriver in places indicated in the owner's
manual. Be careful; the plastic tabs that hold the parts of the fob
together break easily. In some cars, there could be some tiny
screws or other parts that are easy to lose.
When replacing the battery, watch for the way it's installed. One
side of the battery is marked with the "+" sign. It's important to
install the new battery the same way, or it won't work.
If you are not mechanically inclined, visit your dealer; they
should be able to change the key fob battery for you. Typically it
doesn't take more than a few minutes. We checked with several
dealers and the prices we got were within $10. A key fob doesn't
need any programming if only a fob battery is replaced.
