I have an S90 and recently bought a "new-ish" remote from a Volvo mechanic for $50.
He showed me how to program it:

1. open the car and get inside, making sure to close all doors, hood and trunk;
2. Turn the ignition on and off 5 times (don't turn the car fully on.. only to the 2nd ignition switch position);
3. On the 5th ignition turn, hold down the lock button for a few seconds;
4. Start the car for about 20 seconds, then turn off;
5. Test the remote.

I hope that works for you.
Please let me know how that works for you.


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1998 Volvo S90 17" C70 wheels and only 50K miles. Long way to go!!