If you have a Mazda and can’t or don’t want to go to a dealer, there is one good YouTube video that helps but you have to be very careful.

You may be able to take yours apart and use the physical key to open your doors before you can get the battery replaced.

The Fob has a hidden key that opens the door. In theory you can get in and drive away with a dead Fob.

Put in the wrong way and it won't work, positive side is usually on the top.

for a little more you can get a lifetime replacement.

You have a car like my BMW. I asked the shop guys to replace the batteries and they handed them back to me and said they are designed to charge while the car is on. I have one key that locks and unlocks the doors and sometimes starts the car, the spare key never works with the door locks buy always starts the car.

When the one that sometimes starts the car actually does start the car, I feel obliged to take a little drive to charge it up. I worry about the day when I decide to drive it after leaving it sit for a couple weeks, that neither key would work.

Believe you was given some bad information, better ask around at battery or lock shops before
the keys give you trouble. Battery shop would probably be less expensive. Could do a google
search on your make/model/year and key battery. Let me know what you find out.

I have been skeptical about that but never took the time to look it up. True, batteries burn out even if they are rechargeable.

I'll have to add that to the list that suddenly materialized in the last half hour!

BMW says that the battery in the key recharges when driving, but the battery wouldn't take a charge. I followed a youtube video on how to replace the battery - which is to cut the key at the seam with an exacto knife, replace the battery, and weld the key back together with a soldering iron. Worked great, took about 20 minutes and cost $8.99 for the battery.

I'll keep that advice in mind I might be needing it before long. I know people who could do that for me too. Now that the roads are crappy, though, it will stay parked unless the roads are dry. The 4WD sensor won't turn it off once activated and I have to take it to the shop and after $80... And I HATE anti-lock brakes, my other vehicle is not ruined by having them, an older 4Runner.



And welcome to DU!

As others have said, make sure you properly insert the new battery. If you still cannot unlock/lock the doors or open the trunk, you may need a new key fob.

If the battery replacement works, be sure to replace the batteries in any other key fobs for that vehicle.

If you have to replace the key fob, there are plenty of aftermarket key fobs, but I recommend going with an OEM. On most vehicles, programming is relatively easy (Google the year, make and model of the car and you might find the actual procedure). Make sure you do keep the old key fob; if it was originally programmed to the car when new, you may need this key fob to program others in the future (Ford key fobs work like this).