Doesn't your '95 have the 2 diagnostic boxes next to the washer fluid fill tank? I know that some did, but mid-year they changed the design and so some don't. If yours doesn't then Volvo was getting ready for '96 when OBD-2 became standard, and so YES is the answer unless your car is from Canada, in which case there may not be either option. 850's exported to Canada can be a pain and a lot of times won't pass emission testing in the U.S. because there isn't a universal way to read the codes or even check them, from what I've read.

If you have the diagnostic boxes, consider yourself lucky! These little "gems" are much better than an OBD-2 tool which will only tell you emissions and engine codes...your boxes will tell you much, much more like the ECU functioning.
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1998 S70 T5 Emarald Green Metallic, 2004 V70 2.5T Ruby Red, Previous Owner of Black '94 850 Turbo Wagon