I had the same thing with my '95 855T. Chime and courtesy light in the driver's footwell would stay on, but sometimes slaming the door would get it to go off. Mine was not related to a CEL light, but was the microswitch in the driver's door latch (part of outside driver's door handle, not part of the interior handle). First I would pull the codes for CEL, just to be sure that they don't tell you something about this - possibly part of something else entirely. If codes don't refer to door, then probably it is the micro switch.

There are actually two microswitches in that latch, I think. One for the alarm, and one for the lights/open door warning. You can buy just the switch you need, but then you have to wire it into the harness at the latch. I did it that way, and it wasn't very hard once the latch was out and on my workbench. The separate switch cost $40-50. if I remember right. Alternative is to buy the whole assembly, but that is much more pricey.
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Mike Sullivan ('95 855T (88k), '98 V70XC (92k), '95 855 NA (135k). Past Volvo's: '85 744 (256k), '86 245 (165k), '86 245 (195k), '88 745 (208k), '91 745 (196k), '93 965 (147k) .