The Volvo keyless entry remote control must be reprogrammed if its batteries go dead. You may prefer to avoid having your local dealer reprogram it for around £97 per key. If you don't have the owner's manual to read the programming instructions, unfortunately the Volvo manuals aren't available online for free. Further complicating the matter is that all Volvo car models with owner-programmable fobs were discontinued by 1998. Furthermore, the instructions vary between models. Therefore, trying to program the remote control on your own may be a matter of trial and error.
Make sure all doors are closed, as well as the bonnet. Make sure the tailgate or boot is locked. Get into the car and lock all doors.
Insert the key and turn it from the insertion position (position I) to the "on" position (position II - not the "start" position) five times. In other words, all the dash lights come on, but the engine doesn't start. When you turn the key to ON the fifth time, leave it there. You have 10 seconds to perform this whole step.
Hold down each remote button for a second or two, so the car identifies those buttons as the ones to respond to. If you want multiple remotes to work for that car, you'll need to hit the buttons on each of them in rapid succession (all within 5 seconds) as well. You can program up to three remotes per car.
Get new batteries if the above doesn't work, and try it again. If you already have new batteries in the remote, then proceed to the next step.
Press and hold down the odometer reset button.
Turn the ignition switch to the RUN position.
Release the odometer button while the service reminder light (SRL) flashes. Don't wait until the flashing stops to release the odometer button. If you did that, you waited too long.
Turn the ignition off.
If your alarm doesn't arm when you lock the car with the remote control, try locking with the remote with two rapid-succession presses.
Australian Volvo models from '93 to '98 do not use Volvo remotes; they use a different brand. The remotes aren't owner-programmable and must be programmed at the dealership.