Yes, a possibility is the fuse in the Overvoltage protection relay (what Ron J called the transient surge protector), which is plugged into the electronic control module for the ABS.

Ron wrote that it's on your firewall, but if your car isn't a '91 or '92 (you didn't specify in the pulldown under the subject line) it could also be inside a metal pocket hidden under the carpet beneath your front passenger seat if the car is a '93.

On my '93, after the fun of searching for it (it's pretty well hidden), I just had to clean the contacts on the fuse to get the system to return and the light to go out.

Sometimes though, the overvoltage relay goes bad (not just the fuse) and you need a new one. Trouble is that it's no longer available from Volvo, so you'd have to search for a used one.

[edited afterward: I acknowledge after a second look at your original message that you did state that you have a '91 (lucky for you, because it's easier to reach the relay).]