Changed battery now key fob doesnt work - 2000 Volvo S40

check battery new doesnt mean free from defects --try reprogramming --try other key fob--test ignition system--

retry replacing battery new doesnt mean cant be defective if it is good than fob needs a relearn different cars have different relearn that you can perform but if the fob has other features such as start that will have to be done at dealer ----
Free Keyless Remote Fob Entry programming instructions procedures for all... look up your vehicle and will have instructions one how to program fob --will also tell if need to be done at dealer

Tracy:

Have you replaced the battery in the fob? After replacing the battery in the fob, the car owner's manual will tell you how to re-program the fob to the car.

Put key ignition press unlock or lock 2 times then turn key to accessory position within 30 seconds. Your FOB should work properly.

look at the fues box at the fues if this don work put you key in the to start the car hand press the fob this will set it

Vehicle key fobs work on a continuosly and randomly changing frequency so that no ones key fob should open anyone elses cars. Whenever you press the buttons, or someone unlocks your doors, the frequency is changed. The fob and computer in the car have a few codes stored so that if you press the button too many times out of range of the car it will still know what frequency should be transmitting. However if your battery dies, or you press the button too many times while out of range, you Fob and computer will be out of sync.

Long story short you may need to have your Fob re-programmed. You may fine this info in your owners manual, but will probably have to go to the dealer.

The other issue it could be is something i have heard of a few times for the chrysler FOBs, the solder in the fob that holds the connection for the battery may have broken, which will mean your battery is not connected right. You may want to consider popping it apart and taking a look to see if the solder is cracked at all.

Hi.
I have a clio II, 2001, i have the same problem and i fixed it.
Don't know if will work for you but here it goes:

1 - no key in ingnition
2 - press the unlock button in console off the car for about 10 seconds(dont let go)
3 - it should work the central doors one time and then 2 times( hear)
4 - press the remote a few times until it starts working

It worked for me hope the same for you.
Please tell me if it worked and pass the message.

Good luck

you may have to reprogram it. check your owners manual

I'm more familiar with Range Rovers and Saab's when it comes to key fobs but if you changed the battery you have to re-program the key fob. If you do not have an owner's manual that can take you through the steps you might want to try: push and hold the lock button on the key fob, put it in the driver's side door and turn to lock. With the button still depressed turn back to open, remove the key and release the button. If this doesn't work check any and all fuses associated with your system and last but not least you could take it to a dealer. Good luck!

if it like the mondeo's,you only get 20secs' to change the battery or you lost the code and have to reset it. im not sure if reset code is the same for focus tho.